Quantifying the Economic Burden of
Achilles Tendinopathy
H.L. Douma
∗Supervisors: Prof. Dr. R.H. Koning; Dr. J.O. Mierau
Faculty of Economics and Business, Rijksuniversiteit Groningen Email: H.L.douma@student.rug.nl
This paper presents an estimation of the costs of Achilles Tendinopathy for the Netherlands for the year 2015. The analysis consists of a calculation of the monetary direct medical costs, and of an estimation of the burden of disease expressed in Disability Adjusted Life Years (DALYs). Due to data limitations is opted for an approximation of the true DALY value by indicating a lower bound and an upper bound value.
Results: total direct medical costs for 2015 were approximated ate15.5 mln. The DALY range is estimated at minimum 97.78 and maximum 9,450.38. Keywords: Achilles Tendinopathy; Burden of Disease; Cost of Illness; Disability Adjusted
Life Years; The Netherlands 2015
1. INTRODUCTION
Tendinopathy is the general term used to describe chronic degenerative tendon disorders [18]. Tendon disorders in general are estimated to cause 30% to 50% of all activity-related injuries [18] [25] and are often related to overuse. The Achilles tendon is among the most sensitive tendons to overuse injury [38]. Overuse injury of the Achilles tendon is a problem frequently acknowledged for active sport participants [2] [37]. Achilles tendon injuries typically result in forced suspension of the sporting activities for extensive periods of time and may impact activities in daily life [46]. Treatment of tendon injuries is often difficult and a broad array of possible treatments exists [18]. Consensus regarding the most appropriate or effective treatment is lacking [46].
From the above can be derived at best that the burden of Achilles tendinopathy is large. Through quantification of the burden the gravity of the injury for the Dutch population can be assessed better. This study aims at a twofold quantification of both the bur-den and the monetary costs of Achilles tendinopathy for the Dutch population over the year 2015. As such this study is positioned in a health accounting frame-work.
Health accounting studies are often used for guidance when health research priorities are determined. Since its introduction in 1990, the Global Burden of Disease (GBD) framework has been the principle instrument of
*s1992473
measurement in health accounting. The GBD study mainly aims at classifying a large selection of diseases in terms of estimates of their respective impacts on mortality and disability at the country level.
Nowhere in the GBD study tendinopathy is
mentioned as separate entity. Instead, tendinopathy is included in the category other Musculoskeletal (MSK) diseases. The other group however contains a large variety of injuries and diseases which are likely to vary a great deal with respect to their respective severities and burdens of disease. Whether the other MSK injuries can indeed be conceived as comparable cannot be known if the separate burdens are never being calculated.
This paper represents the first effort of estimating the burden of Achilles tendinopathy in the Netherlands for the year 2015 and is as such a first step in the identification of separate burdens within the group other MSK. Outcomes of the study may yield additional insights in the ranking of Achilles tendinopathy in the GBD study, and in its relative weight within the other category. The outcomes may provide additional information to be used in policy guidelines since a more complete set of information may contribute to a more efficient allocation of resources.
Medical cost studies and estimations of burden of disease rely on health economic theory. Health economics is a complicated subject as it involves the combination of knowledge from several fields of expertise. It is as such an interactive field of research which involves collaboration of researchers with different backgrounds. Given the interdisciplinary character of the analysis, this study will necessarily have to rely heavily on knowledge provided by others.
Extrapolation of knowledge from various sources is however severely complicated since there are few aspects of health economics in general and cost-of-illness studies in particular that have not been debated. It might be even so that the only notion that enjoys a broad and general consensus in all fields involved, is that indeed cost-of-illness and diseases should be measured, and that calculations can be put to use in setting guidelines for policy and directing medical innovations. Stemming from the ongoing discussions there exist a broad array of methods, instruments, and a variety of measurements clouding the overall field of research accordingly.
On almost all of the issues in health economic mod-elling and cost-of-illness studies has been conducted separate research. Therefore entering into an in-depth analysis of all the issues involved will go beyond the scope of this paper. The most pressing issues will be discussed with special attention for problems related to application. For the interested reader additional information can be found in the supporting literature.
In order to eventually formulate an answer to the core question, a pragmatic approach towards multiple issues has been taken. The choices and the resulting assumptions will be discussed carefully. However, in order to not produce a lengthy paper with needless digressions, in most of the cases the numbers and calculations as presented in the literature will be adopted without elaboration on the respective methods and choices made by the cited authors. It is important to note that the efforts of this study are mainly aimed at the assembly of findings from various fields of research so as to compute an overall calculation. For this study was opted explicitly not to compose and use data from own construction, since construction of new data (e.g. surveys measuring productivity loss or measuring degree of pain) would require extensive medical knowledge of the injury and access to (confidential) patient databases.
Zorginstituut Nederland formulated specific guide-lines for the format and guideguide-lines for economic eval-uations in health care. 2 The guidelines are aimed at
facilitating a more uniform design of economic
evalua-2Provided on-line at:https :
//www.zorginstituutnederland.nl/pakket/werkwijze + pakketbeheer/beoordeling + geneesmiddelen/economische + evaluatie
tions. Uniformity of studies would increase mainly their comparability which will ease their potential use in de-termining policy.
In these guidelines specific attention is devoted to the different types of costs that should be included in different types of analyses. Different types of cost are appropriate mainly with respect to the costing perspective that is chosen. For instance if is chosen for the so called medical sector perspective, only direct medical costs are to be included. If however is chosen for a societal view, more types of costs are to be measured, such as productivity related (or sometimes called indirect) costs. These distinctions between direct and indirect costs are familiar from an economic perspective. However, with respect to the societal perspective the guidelines furthermore recommend the inclusion of a separate other category to capture costs accrued by individual patients and their families during the disease process - as for instance travel expenditures, time costs, or costs devoted to special dietary requirements.
This study will make use of the guidelines provided by Zorginstituut Nederland. However, due to a lack of data choices had to be made to follow only part of the recommendations. Consequently this study will provide a monetary costs evaluation from the perspective of the medical sector as opposed to the recommended societal perspective. Considering this societal perspective is the one generally recommended, and considering the corresponding importance of the perspective’s methods in the existing literature, this study will discuss relevant literature with respect to productivity related costs in the theory section even though a specific costs estimation for those cost types is not provided. Resulting limitations from this choice of perspective and its implications will be discussed further in section 7.
finally section 8 will provide some concluding remarks.
2. THEORY
Since health economic analyses depend upon knowledge from various fields of research, likewise the theoretical foundations stem from various sources. This section will provide a theoretical framework from which the choices for the economic evaluation will be defined. With respect to the framework needed for economic valuation of Achilles tendinopathy, a diverse body of literature with elements of for instance general economics -i.e. how does health enter in a utility framework, how do we set up a general framework of (medical) cost calculation, how can and should productivity be measured and valued? - applications of health economics, and epidemiological literature regarding disease specific knowledge, has to be considered. In order to keep a structured overview, this theory section will treat literature of different academic background in different subsections. The theoretical framework of this paper will be quite extensive since all choices and assumptions needed for the calculations will be derived from it. This section will start with a general overview of welfare economics and the most common methodological choices, before committing to the epidemiological characteristics of Achilles tendinopathy. By first discussing the elements required in medical cost calculation, the resulting framework allows for the epidemiological section to be more applicative and to assess only the corresponding relevant elements.
2.1. Welfare Economics
Traditionally economic evaluation is based on welfare analysis [19]. In effect, welfare analysis is rooted in micro-economic utility theory. It assumes that individuals maximise utility, and that total welfare is derived from an aggregation of all individual utility in society [13]. In basic micro-economic models, utility (and hence welfare) is derived from both consumption and leisure. Some extensions have been proposed to include health as a separate entity in the utility function, as for instance in the Grossman model [21]. The importance of health for the welfare of the society as a whole becomes easily apparent; societal welfare is derived from individual utility, individual utility depends on health, so then if health levels are assumed to be influenced by spending on health care, optimal health can be best approximated trough optimal allocation of resources in health care. The main complication of this reasoning lies in determining the exact influence of health care spending on health outcomes, and designing an optimal allocation of resources accordingly. The Grossman model assumes a personal trade-off of medical spending and consumption in combination with a time trade-off of time spend on health related activities and time spend on work
and leisure. In practice however, things seem to be somewhat different. Sick people cannot always increase their own health levels, but moreover in the Netherlands heatlh insurance is mandatory and organised accroding to the so called deductible system. In this system individuals face the full cost of care only to some specified limit, and the insurer pays for all costs accruing after that. As individuals effectively do not pay for those expenditures exceeding their fixed amount, and those units of medical interventions will be provided non-regarding the costs, this system is likely to influence decision making on medical goods consumption.
A large part of the national health burden is borne by the government. In 2015, the Dutch government committed to e72.9 billion euro on health care re-lated expenditures [47], which amounts to 28.1 % of total government expenditures in 2015. Economic calculations and welfare analyses can be used by the government to provide guidance and justification of this large amount of spending.
Whereas many economists perceive the utilitarian approach of welfare economics as the theoretically correct approach, it does present the researcher with some serious methodological issues. Most notoriously, utility does not lend itself very well for cardinal measuring and as such is not directly interpersonally comparable [56].
given the baseline outcome) or compensating variation (that sum of money that the individual would be willing to pay to reach the baseline under the alternative). However, those values are not easily computed for a representative sample, and moreover, the approach requires that individuals are able to value their own health status in monetary terms.
Measuring health in itself is one of the central concerns in health economic evaluations, which will be discussed in the following subsection.
2.2. Measuring Health
One of the most straightforward ways used to measure health is the use of life expectancy, generally expressed in years. The idea is that a disease influences a person’s life expectancy, and hence can be used as an indicator of health. An individual may however value some life years different from others, depending on for instance current age or stage in life and the state of health in those years to come. In other words, people might attach different values to different years, and moreover those valuations are subjective. In health economic research Health Adjusted Life Years (HALYs) are considered popular population health measures. The two most common in use will be discussed in the subsections below.
2.2.1. Quality Adjusted Life Years
In the late 1970s a solution to the above was developed by means of a measure that combined the quantity and quality of life years, the Quality Adjusted Life Years (QALYs). The measure reflects individuals’ preferences for health status [26], and could as such be employed as a quantifiable measure of health outcomes [19]. If QALYs relate to health outcomes, they could be used as a representation of health benefits from certain health care interventions. However, some argue that - in line with expected utility theory - QALYs are a mere representation of preferences associated with a set of given health outcomes [45]. Before QALYs can be at the base of a solid preference structure, some assumptions will have to be made, specifically the well known assumptions of completeness, transitivity, continuity and strong independence [19]. Only if all those assumptions are met, the QALY can be justified as a true representation of individual preferences of health status (ceteris paribus). As Bleichrodt (1997) [7] shows, the QALY can indeed under certain assumptions reflect a cardinal ratio scale, by which it fulfills its function of interpersonal comparison.
Extensive empirical evidence does however suggest that expected utility theory is not the most adequate description of individual behaviour under uncertainty [19]. This would suggest a more appropriate interpreta-tion of QALYs as a measure of health outcomes without linking them to individual preferences. 3 In the
litera-3For an extensive treatment of the use of QALYs under this
interpretation, see Broome, 1993 [9].
ture extensive discussions can be found regarding sev-eral issues surrounding QALYs, with respect to concep-tualisation [9], ethical implications, and distributional issues [53].
In practice, QALYs are often used as a measure of benefits or health gains from specific health interventions or treatments and are hence considered a useful tool in computing benefit or cost-effectiveness analyses when assessing the improvement in quality adjusted life expectancy [52].
2.2.2. Disability Adjusted Life Years
Another measure often used is the Disability Adjusted Life Year (DALY). As opposed to the quality of life captured by the QALY measure, DALYs measure the burden of disease, and have as such become the standard metric to quantify health burden [23]. As defined by the World Health Organization (WHO), the DALY is a health gap measure. The measure combines the burden of actual life years lost due to disease with the equivalent years of healthy life lost resulting from the incidence of diseases and injuries. Intuitively, one DALY can be thought of as one year of healthy life lost due to disease. As such, the calculation of DALYs consists of two separate parts:
• Years of Life Lost due to premature mortality (YLL)
• Years Lost due to Disability (YLD) 4
The first part of the calculation hence captures the burden of premature mortality, and the second part quantifies the health loss for all non-fatal consequences of disease.
Since DALY is primarily a measure of disease burden [52] it is more straightforward to use in economic cost evaluation than the QALY. In the Global Burden of Disease (GBD) framework, burden of disease is accordingly presented in DALYs. The degree of disability resulting from disease or the loss of functioning of the second part, is incorporated in the measure by a disability weight. QALYs are computed also with the use of weights (quality of life weights), the main difference however being that the latter weights are composed on a scale where 1 represents pure health and zero corresponds to death, whereas the former in accordance with the conceptualisation of burden is calculated with a scale where 1 represents death, and 0 represents the state of full health. Therefore higher DALY scores correspond to worse outcomes, and higher QALY scores to better outcomes or higher benefits.
One of the central critiques of DALYs is the contextualisation of disability within a particular cultural environment [51]. This mainly concerns potential cross-cultural variability weights, and hence cross-cultural and cross-country comparison of disease
4The formulas for calculation of DALYs are presented in the
burdens. As Salomon et al. (2013) propose, it seems reasonable to assume that health loss associated with different diseases and states of health is to a larger extent universal than is is welfare loss. This assumption is mainly based on the argument that welfare loss will depend largely on a set of individual preferences, which on its turn will be largely determined by social context. In practice, the DALY estimates of the GBD 2010 study are based on a set of standard disability weights.
5 Computation of the appropriate values involves the
contribution of many expert valuations, such as disease specialists and epidemiologists [35].
With respect to Achilles tendinopathy however, disability weights have not yet been established. Therefore here the weight will be proxied using estimates of other conditions that have been reported. Section 4 will elaborate on this choice.
2.3. Cost of Illness versus Burden of Disease Within the field of health economics a large number of different types of economic evaluations have been proposed, among others: Cost-of-Illness studies (COI), Cost-Minimisation analysis (CMA), Cost-Effectiveness analysis (CEA), Utility analysis (CUA) and Cost-Benefit analysis (CBA) [26]. In general it can be said that COI studies have mainly a descriptive function in that their main aim consists of identification and quantification of costs, whereas the other methods mentioned are often employed in studies with a more comparable objective. Those studies are used for instance when the aim of the analysis is to compare different types of treatment or to assess (cost) effectiveness of an intervention. Central to all evaluations mentioned except for COI studies, is that their computation involves some kind of outcome measure. COI studies are in essence to most basic type of economic valuation in that their main aim is to identify and quantify economic cost of illness without attaching any normative or comparative qualities.
Cost of illness is often referred to as burden of disease (BOD). The terms are however not entirely equivalent. The intuition behind substituting terms for economic cost and economic burden seems straightforward in general, but it must be noticed that in terms of COI and BOD studies intertwining the two terms may cause some confusion. In general, COI studies refer to a calculation of the monetary costs of the disease of interest. Therefore most COI studies include roughly the same items:
• Direct costs - Medical costs borne by either the health care system or the patient and his family. • Indirect costs - Generally expressed in productivity
losses.
5For the GBD 2010 study a comprehensive study regarding
appropriate disability weights for the 289 disease and injury causes has been conducted by Salomon et al. [51] (published separately 2013) through a large scale empirical investigation.
• Intangible costs - (Psychological) costs of pain and suffering.
The eventual goal of a COI study is to value the separate items and to compute overall costs by simply summing the values. The main difference with BOD studies is that those tend to aim at estimating burden expressed in DALYs. By burden is then not meant a monetary cost, but instead a burden on society in terms of health loss. Burden of disease studies are consequently often aimed at formulating a ranking of diseases based on their respective severities expressed in health loss for society.
Since both approaches hold their own appeal, in this study estimates for both types of burden will be provided in order to get the most complete insights.
2.4. Assessing Cost Components and Methods
in COI Studies
2.4.1. Measuring Productivity Losses
Fassbender and Jacobs (1998) [24] define indirect costs as 'the costs of those resources for which no payment is made, but for which there is an alternative use that is of value to someone.6' Typically, indirect costs relate to foregone employment due to sickness absence and are hence often measured in terms of productivity losses for society. Broadly there are two main approaches to estimate productivity lost: the Human Capital Approach and the Friction Method [26]. Both approaches base productivity losses on present and expected future earnings. The main difference is the perspective of analysis. The human capital approach takes the employee’s perspective, and defines an hour not worked as an hour lost. The friction method takes the perspective of the employer, and estimates productivity losses by counting hours not worked until someone else takes over [57].
There are three main ethical and methodological objections that are often raised with respect to the human capital approach. The first is that the method equates someones worth to his productive capacity in paid labour. This implies that subjects not active in paid labour, such as children, the elderly, the unemployed, and those active in low labour, represent less value to society than their active and high paid counterparts. This represents not only an ethical issue, but causes somewhat of a paradox in health assessments, since those that provide - in these terms - the least value to society are the most likely to be in need of health care and hence cost the most [26]. Then the second objection involves that if productivity losses are approximated by average earnings, those losses calculated are likely to overestimate the real loss. The main reasoning is that if employees are absent for some days only, high productivity losses for firms are unlikely as workers’ tasks may be taken over by colleagues, or
as workers are able to catch up after return. Thirdly, the human capital approach potentially counts loss of productivity twice, since it counts both mortality loss and absenteeism loss as equivalent to productive years in earnings. This issue is especially likely to occur when the demarcation between death and absence due to sickness is not transparent [26].
Taking into account these objections, Koopmanschap and Ineveld (1992) [30] developed an alternative approach. Their main argument against the human capital approach was that if applied, an estimate of potentially lost production was provided, not of actual productivity lost. The authors pose that losses due to sickness will be confined to a limited period of time needed to adapt to the changes. That adaptation period is defined as the friction period [30]. The friction method involves calculating production losses during the friction period, sometimes with inclusion of the costs incurred when selecting and training new employees in case permanent replacement of the absent employee is necessary.
Objections have been raised with regard to the appropriate length of the friction period. The length will depend on the situation on local labour markets which determines the availability of labour. According to Van Houten (2010) [57] in empirical use, the appropriate length of the friction period is generally taken to be six months [57]. However, Zorginstituut Nederland recommends the use of a standard period of 12 weeks. Another objection is that only if the replacement worker was previously unemployed, the estimation of the losses through the friction method is valid [57].
Since the two approaches calculate productivity losses over different time periods, the estimates differ greatly. Based on their respective objections, the human capital approach is often accused of over-estimating costs, whereas the friction method might under-estimate them. For estimations of short-term absenteeism (i.e. under six months) the two methods provide roughly the same results [57]. Convincing empirical evidence to determine which of the methods is the most appropriate is lacking, and both continue to be used in spite of their limitations.
The relevance of productivity losses with respect to Achilles tendinopathy has not yet been established. Mainly the extent to which productivity losses will occur with respect to Achilles tendinopathy is unclear. Further considerations regarding application of the productivity measures discussed for the case of Achilles tendinopathy are presented in section 4.2.3.
2.4.2. Presenteeism and Absenteeism
Presenteeism is used to indicate and measure produc-tivity loss when work abilities are compromised due to illness but when no direct absence results. The implicit assumption is that even when present at work,
produc-tivity deteriorates due to pain and inconvenience. Pre-senteeism is however a controversial concept. Where the conceptualisation and theoretical presence of pro-ductivity loss is often recognised, quantifying presen-teeism is complex [14]. Considering its conceptualisa-tion as a measure relating actual performance to possi-ble performance, presenteeism instruments rely on self-reported levels of productivity. Broadly three distin-guished methods of measuring presenteeism have been proposed [41]:
• Assessment of perceived impairment.
• Comparative productivity, performance and effi-ciency.
• Estimation of unproductive time while at work. Where the first item represents the most common and widely used approach in empirical research [41]. Over the years several questionnaires have been devel-oped for measurement of these types of self-reported measurement. Of these questionnaires, the WHO Health and Work Performance Questionnaire (HPQ) is one of the most widely used. It was developed by the WHO as part of the GBD initiative [33]. Available on-line at the website of Harvard Medical School 7 the HPQ and an explanation of the computation of absolute and relative presenteeism scores can easily be found. The scores have however not been computed for many diseases, and moreover, the HPQ measures only chronic conditions. Loeppke et al. (2007) [33] devel-oped a ranking of 27 health conditions8 based on their
respective impact on overall productivity due to both absenteeism and presenteeism for four employers. The ranking indicates which conditions contribute to the largest health burden for the four employers analysed. The study does not however provide generalisable or standard values that can be used in the empirical investigation of disease specific absenteeism and pre-senteeism related losses. Overall, there does not appear to be one gold standard in investigating presenteeism related costs. This might have to do with the fact that the different questionnaires rely on individual’s self-reported productivity losses. Therefore outcomes and scores will likely depend on several sampling- and cultural or societal issues.
Absenteeism is used to indicate the productivity costs arising from a sick worker being absent [11]; as is in fact done in both the human capital approach and the friction method. Often absenteeism related costs are calculated from multiplying the amount of hours absent on a yearly basis with the average workers’
7http://www.hcp.med.harvard.edu/hpq/
8Allergy, Aniety, Arthritis, Ashtma, Back/Neck pain,
hourly wage. Empirical analysis of the concept of absenteeism is mainly aimed at estimating the overall level of yearly absenteeism related productivity costs at the country level [12] or at the company level [33]. Applied to specific diseases productivity losses are often reported based on absenteeism, generally however no exact presenteeism related cost estimates are provided mainly due to methodological issues.
There do not yet exists absenteeism and presenteeism scores indicating losses specifically due to Achilles tendinopathy. There has been done some research regarding productivity losses and presenteeism due to the broader category of musculoskeletal diseases for a sample of health care professionals [10]. The research however concerns such a specific sub sample of individuals that the outcomes are not likely to be generalisable to the overall population. Results indicated that for moderate musculoskeletal conditions work-output per worker was 5% lower [10]. Which MSK conditions were specifically included in the research and which injury contributed to what part of the productivity loss was not separately reported. Due to these issues, the results presented by the study are deemed not to be generalisable and hence not considered to be applicable in this analysis.
An important assumption will be made here that with respect to Achilles tendinopathy a negligible amount of absenteeism related productivity costs will arise. The assumption is based on the expectation that workers will not report entirely sick due to pain of the Achilles tendon. Therefore the model presented in section 3 will take into account presenteeism related costs only.
2.4.3. Activity Impairment outside Work
Calculations of presenteeism and absenteeism related productivity losses are generally based on assessing losses with respect to paid work. As productivity losses are conceptualised as being caused by to pain, discomfort or loss in functioning, the same types of losses are likely to result in unpaid work restrictions. For simplicity here we will assume that the main body of non-paid work applies to household production. In addition to unpaid work, other activities outside work are also likely to be affected by disease. These activities include leisure activities, or activities with respect to recreation and hobby [8].
With respect to measuring productivity losses of unpaid work, Zorginstituut Nederland provides a guideline for the hourly replacement costs for a non-paid worker. This implies that in calculating productivity losses of paid and unpaid work the same methods of presenteeism related productivity losses can be used. The calculation for unpaid work simply involves multiplication of the amount of productivity lost with a different cost per hour. An alternative is mentioned by Boonen et al. (2006) [8], who instead use the hours of help required by family and friends (on a yearly basis) as
a proxy for unpaid productivity loss. As an extension paid household help could be included in these kind of calculations [15]. The extent to which productivity losses with respect to unpaid work will arise will again depend on severity of the condition.
With respect to impact of disease on leisure activities quantification of the burden is more complicated. First it should be determined to what extent patient-and disease specific characteristics are of influence on engagement in various leisure activities. Second it should be assessed how the disease or injury induced change in leisure activities affects individual utility. As the disease or injury prevents the patient to engage in his preferred activities, the change in leisure activities is expected to enter the utility function negatively. Therefore this change represents a deterioration of quality of life. In order to quantify it should be assessed to what extent a shift towards other leisure activities results in reduced quality of life. In other words, the magnitude of utility losses arising from the shift from preffered activities to less preferred ones should be determined. A last step towards quantification would then be to attach a monetary value to individual utility loss. Several complications arise. First of all, preferred leisure activities will differ for each individual, and the impact of a change will also result in different utility changes for each. As discussed previously in section 2.1 about welfare economics, valuing utility does present us with some particular challenges. These general issues again apply to the incorporation of changes in leisure activities in cost calculations.
Changes away from preferred leisure activities certainly do present a cost to affected individuals expressed in reduced quality of life. Conceptual difficulties and lack of data however prevent the costs from being generally estimated [22].
2.4.4. Intangible Costs
As mentioned in section 2.3 intangible costs are often recognised as one of the three main cost components in COI studies [19]. Intangible costs are those costs associated with pain and suffering [36]. From this definition can be derived that in effect intangible costs are costs measuring loss of quality of life. Inclusion of intangible costs in the monetary cost evaluations of COI studies would require attaching monetary values to either loss of quality of life or disability measures. Attaching monetary values to human life and health is a sensitive subject and often results in normative discussions. There have been some attempts to transfer quality of life measures to monetary values using willingness-to-pay methods. 9 With respect to policy and resource allocations these kind of monetary measurements and corresponding normative discussions contribute to the discussion of the maximum amount
9See for instance Pinto-Prades, Loomes and Brey, 2009 [44];
that should be paid for a marginal QALY gained [5]. Leaving those normative issues for other research to discuss, in this paper no monetary cost evaluation of intangible costs will be made. We will assume here that as intangible costs are closely related to the costs of health loss, the most straightforward metric is to leave burden of disease expressed in DALYs without converting them to a monetary value. This implies that in the monetary cost calculation intangible costs will be left out all together.
2.4.5. Incidence Based approach versus Prevalence Based approach
In COI/BOD calculations we can distinguish between the incidence and prevalence based approaches. The approaches differ in the way that epidemiological data are used and in time frame chosen. The prevalence based approach is aimed at estimating the burden of a disease over a specified period - typically a year-and hence uses number of annual deadly incidents and other reported cases on an annual basis to calculate. The incidence based approach refers to new cases arising in a time period, and using these data estimates total lifetime costs from commencement to disappearance. Hence prevalence based approaches are generally employed to measure COI in present and past years, while the incidence based methods aim at estimating present and future costs from the cases arising in a given year. Considering this inclusion of costs for years to come, the incidence based approach generally yields higher estimates [27].
Tarricone (2006) [55] summarises which approach is the more appropriate to use for different types of research. Considering her checklist, for this study the prevalence based approach seems the best fit, since the prevalence based approach is mainly aimed at:
• Raising awareness for conditions whose burden is suspected to be somehow underestimated by policy makers.
• Providing guidelines for design of cost containment policies by providing insights in the major cost components.10
2.4.6. Top-down versus Bottom-up approach
Broadly there are two ways of cost counting in COI studies. The top-down approach (gross-costing) measures the cost of a condition as proportional to exposure to disease - or risk-factors. The bottom-up approach (micro-costing) consists of two steps. The first step is to itemise all health inputs used with regard to the specific condition, and to estimate unit costs of different inputs. The second step exists of calculation of the total costs through multiplication of unit costs and quantities. In effect, the bottom-up approach is hence a summation of each single cost component, and often
10For the complete reasoning and arguments, see the article
by Tarricone, 2006 [55].
regarded as the actual cost of contributing services. Whereas the top-down approach is often considered to be somewhat simpler to use, the bottom-up approach generally leads to more precise estimates [55].
2.5. Epidemiology of Achilles Tendinopathy In order to make an accurate estimation of the burden of Achilles tendinopathy, many insights from the epidemiological literature will be required. Information on diagnoses, duration, different treatments and their costs, but also more concrete values such as prevalence rates and disability weights are very much needed. In this section, insights from the literature regarding several elements of the epidemiology will be discussed. 2.5.1. Definition of Tendinopathy
A first step required for a more in-depth analysis is establishing a workable definition of tendinopathy. Traditionally tendinopathy is often referred to as an inflammation of the tendon, but this is in fact not the correct medical definition. The medical dictionary defines tendinopathy as any disease or condition that affects tendon structure or its function. 11
The correct term to refer to inflammation of a tendon is tendinitis [43]. The general ideas surrounding tendinopathy would imply that tendinitis would be a major cause of tendinopathy, but in reality this appears not to be the case [6]. As an addition to tendinitis, there is the term tendinosis. Many cases indicated as tendinits are in fact the result of tendinosis [43]. Tendinosis is a failed healing response after damage of the tendon [43], which results in a thickening of the tendon [34]. When cases of tendinosis are closely examined, it even appears that there are no signs of inflammatory cells at all [29].
Tendinitis refers to the condition of inflammation of the tendon itself [43]. It was common thought that this inflammation, or tendinitis, was at the base of the symptoms of tendinopathy. Some current histological studies however do not longer support these thoughts [6] and negate inflammatory processes as cause of tendinopathy [43].
It is however still common to call Achilles tendinopa-thy Achilles tendinitis. These confusions and miscon-ceptions may be an indication of the need for new in-sights, mainly since the knowledge that tendinopathy might not be an inflammatory process leads to contro-versy with regard to its treatments.
The majority of cases of tendinopathy seem to result from overuse and repetitive motion [20] [54]. Therefore the injury is more commonly seen in people actively engaging in sports [34]. Consistent with the cause of overuse, initiation of the activities tend to worsen the complaints. Complaints with regard to Achilles
11Medical Dictionary for the Health Professions and Nursing.
tendinopathy are often referred to as morning stiffness, as the associated pain is often reported to be more severe in the morning [20].
2.5.2. Treatments
In order to list the costs associated with Achilles tendinopathy, possible treatments need to be consid-ered. A variety of treatments has been proposed that can be broadly divided in surgical and non-surgical in-terventions [43]. Surgical interventions are generally considered optional only when conservative non-surgical treatment has not yielded desirable results. Whilst non-surgical management of tendinopathy continues to be the preferred type of initial treatment [46], there is no general consensus whether there is one treatment supe-rior to others [42].
This debate surrounding superiority of treatments can easily be linked to the histological discussion. For instance when considering tendinopathy an in-flammatory process, including anti-inin-flammatory med-ication such as corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDS) as possible treatments seems straightforward. These treatments have however become debated taking into account the discovered dif-ferences between tendinitis and tendinosis, and their respective roles in causation of tendinopathy.
It would lead too far here to provide an extensive listing and discussion of the complete range of possible treatments. 12 In order to gain insights in separate cost
categories, it seems reasonable to broadly divide into:
• Rest
• Ice or Cryotherapy • (Eccentric) Excercises
• Pharmacological interventions (e.g. corticos-teroids, platelet-rich plasma, growth hormone) • Surgical interventions
Since there is such a broad arsenal of possible medical treatments, the estimation of costs becomes severely complicated if there is no consistent way in assessing what percentage of patients get treated with which treatment. There are no studies yet that provide such information. Moreover, the costs of the various treatments differ substantially. Taking an average could hence not be justified on any grounds but convenience. Of the feasible options reliance on expert opinions and actual reported health insurance expenditures was deemed the most accurate.
When in pain, it is assumed that patients will visit a general practitioner first, who will mainly use treatments of items 1 and or 2, or refer to a physiotherapist (item 3). In case those remedies are not sufficient, the patients may thereafter visit the hospital (items 4 and 5).
12for an overview of non-surgical treatments see Nuttall, 2014
[43] and Rees, 2009 [46].
2.5.3. Severity and VISA-A
Potential treatments and histological definitions aside, in order to compute a proper estimation of costs the severity of the injury needs to be addressed. Only then the impact on individual’s lifes and the amount of DALYs can be computed. As mentioned earlier, disability weights for Achilles tendinopathy have not yet been estimated. Generally, complaints of patients suffering from the injury vary from morning stiffness [20] to general pain in the ankle area.
Robinson (2001) [49], acknowledged the need for a quantitative index to measure pain and function of Achilles tendinopathy, and developed a questionnaire that could serve as an instrument of the injury’s severity: the VISA-A score. Eight questions were used to measure domains of pain, functioning in both daily life and sporting activities. Scaling was such that 100 represents the perfect score. The VISA-A score was estimated for non-surgical and pre-surgical patients as well as for a control group. The mean VSIA-A score for non-surgical patients was reported to be 64, and in pre-surgical patients 44. For the control group the mean score was close to the perfect score; estimated to be 96. The results of this study are hence supportive of expectations that surgery is mostly directed at treating the more severe cases. When rescaled with a factor 100, and compared to the DALY/QALY disability weights, it is immediately apparent that the scaling of the VISA-A is more in accordance with that of the quality of life weights, 13 where pure health is indicated by 1.
Therefore when using DALY calculations, the VISA-A score might be employed to approximate disability weights, but then only if transformed to the correct scaling.
Another option to measure severity would be to ap-proximate disability weights for Achilles tendinopathy by already computed disability weights for instance the weights corresponding to musculoskeletal problems (legs) from Salomon et al., (2013) [51] (Table 1).
Disability weights MSK - legs
Injury Disability weights
MSK problems legs Mild 0.023 (0.013-0.039) MSK problems legs Moderate 0.079 (0.053-0.115) MSK problems legs Severe 0.171 (0.117 - 0.240) TABLE 1: Disability weights musculoskeletal disorders
13As quality of life weights are generally used as outcome
3. METHODOLOGY
This section specifies two models as derived from theory in two separate subsections. In section 3.1 the model to calculate the DALY burden will be presented, and in section 3.2 the model for estimating monetary cost burden is provided.
3.1. Modelling DALYs
To calculate burden of disease expressed in equivalent years lost of healthy life for an arbitrary disease, the DALY burden is defined as the sum of Years of Life Lost (YLL) and Years Lost due to Disability (YLD). The formula takes the form:
DALY = Y LL + Y LD (1)
Y LL = ND× L,
Y LD = Np× DW × T
Where NDis number of deaths in a specified year, L is
the standard life expectancy at the age of death; Npthe
number of prevalent cases, DW the disability weights for a specified disease, and T the average duration of a case till remission or death in years.
With respect to Achilles Tendinopathy, mortality is taken not to be a relevant factor. Since hence by definition ND = 0 in equation (1), the formula for
DALY simplifies to:
DALY = Y LD (2)
DALY = Np× DW × T
Where the second line in equation (2) is obtained by substitution of line 3 from eq. (1).
3.2. Model of Monetary Valuation
In accordance with the main body of cost-of-illness studies and as discussed in section 2.4.4, the intangible cost element will not be taken into account in the model specification for the calculation of monetary costs. The measure of total costs will consist of direct and productivity costs according to:
Ct= {Dt+ It+ Ht}, Ct∈ 2015 ≤ t ≤ 2016 (3)
Where Dt represents total direct costs for year
2015, It are total productivity related costs for paid
work due to presenteeism over year 2015, and Ht
represents the total productivity related costs due to presenteeism of non-paid (e.g. household) work. As with respect to Achilles tendinopathy absenteeism related productivity costs are assumed irrelevant, only presenteeism related productivity costs are included in the model. Specifically:
Dt= n1CG+ n2CP+ n3CH (4)
It= Np× α × T × Yt (5)
Ht= Np× α × Vt (6)
Where n1 represents number of people visiting a
general practitioner, n2 the number of people visiting
a physiotherapist, n3 the number of people using
hospital services, CG, CP and CH the average costs
of medical services received at the general practitioner, physiotherapist and hospital respectively; Np total
number of prevalent cases, α is the presenteeism score or percentage of lost productivity, T the average duration of a case till remission or death in years, Ytis GDP per
Capita, and Vtis value of non-paid work. It is assumed
that n1 ≥ n2 ≥ n3. All subscriptst indicate that the
costs are calculated for a specified period of time, in this case the year 2015. 14
As recommended by the guidelines for health economic evaluations by Zorginstituut Nederland, apart from direct medical costs and productivity related costs also non-medical personal costs accrued by patient and family should be estimated. This other cost category is however not typically included in applied economic cost evaluations. The standard COI studies in general follow the specifications of equations (3) - (6), often however with inclusion of absenteeism related costs. If, following the guidelines, the other category would be included, the model would change to:
Ct= {Dt+ It+ Ht+ Pt}, Ct∈ 2015 ≤ t ≤ 2016 (7)
Where Pt stands for the personal costs incurred by
patient and family, and where the other variables are defined as above. Pt could be further specified as the
sum of direct personal costs15 (CI) and loss of leisure
time (L):
Pt= Np(L + CI) (8)
Whilst the theoretical existence and relevance of the variables Pt, It and Htis recognised here, no
quantifi-cation efforts will be made due to a lack of quantifiable evidence. The calculation of monetary costs will there-fore be based on equation (4).
As a means of further specifying the costing model, assumptions are made regarding the general trajectory of a typical patient through the health care system.
14As an alternative, it could by hypothesised that productivity
losses could be expressed as some function of health as health state is assumed to be of influence of the degree or productivity. For a discussion of this matter see for instance Chatterji et al., (2002) [11]. This issue will here further be left for other, more theoretical studies to explore.
15Direct personal costs could be conceptualised as for instance
Specifically, in calculation of the costs is assumed that every patient first visits the general practitioner (n1),
and that only part of those patients then subsequently visit the physiotherapist (n2). Patients do not
necessarily have to visit the general practitioner before visiting a physiotherapist. The proposed structure is however based on the fact that physiotherapeutic care is often only being reimbursed by health insurers if the patient is referred through a general practitioner. Therefore it is not likely that a large amount of patients seek out a physiotherapist if not referred. Implication for the model is that those n2 patients are counted
twice: once for the costs incurred at the GP, and once for the subsequent treatment at the physiotherapist. Since n1 is taken to be total number of prevalent cases:
n1= Np (9)
It is furthermore assumed that surgical interventions are only conducted if all conservative treatment has failed. Patients are assumed to visit the general practitioner a second time, before being referred to the hospital to receive surgical treatment. This assumption is based on the fact that physiotherapists cannot refer patients to the hospital directly. A number of n3 patients therefore visits the general practitioner
a second time before entering the hospital services. Taking this into account, the formula for estimation looks like:
Dt= n1CG+ n2CP + n3(CH+ CG) (10)
4. DATA
The data used to quantify the models presented in the previous section will be derived from secondary sources. This section will therefore describe mostly where the data come from and what the exact figures are. For a more extensive treatment of all derivations of data and the methods of sampling is referred to the respective sources.
4.1. DALY - data
Following formula (2), in order to calculate the DALY burden, data regarding prevalence rate, disability weight and average duration of Achilles tendinopathy are needed. The following subsections provide the data used.
4.1.1. Incidence and Prevalence rates
De Jong et al. (2011) [17] investigated the incidence and prevalence rates for midportion Achilles tendinopathy in a sample of 57,725 GP registered persons. The count was performed using the computer registrations of general practitioners over the year 2009 using the International Classification of Primary Care (ICPC) codes. A complicating factor is that there does not
exist a specific ICPC code for Achilles tendinopathy. Therefore the researchers searched for the term achil. They stated that a necessary condition for a tendinopathy was that patients reported pain in the Achilles tendon above the insertion. All cases without this description were excluded. Reported results where a prevalence rate of 2.01 per 1000 registered patients,
16 and an incidence rate of 1.85 per 1000 registered
patients. 17 All cases for which the first visit occured in 2009 where counted as incident cases; to the prevalent cases were added those patients who visited before in 2008.
A similar study by Albers, Zwerver and van den Akker-Scheek (2014) [1] reported a prevalence rate of 2.35 and an incidence rate of 2.16 per 1000 person years for Achilles tendinopathy in the year 2012 for a sample derived from the Academic General Practice Groningen. 18 Also here ICPC codes were used to select
the appropriate cases. Inclusion criteria for cases were: • Diagnosis tendinopathy/tendinitis of Achilles
ten-don
• Pain located in Achilles tendon or its insertion on calcaneus
Both studies report similar rates. The slight differences may be attributed to different search tactics, the use of a different (sized) sample, and slight differences in reporting standards between general practitioners.
There are no specific reasons as to why the incidence-and prevalence rates for Achilles tendinopathy would differ in different years, or why they would have either increased or decreased for the year 2015. Therefore here it seems reasonable to approximate the prevalence rate by taking the average of both reported rates, and hence an assumption will be made that no significant differences will exist between the rates of 2009 and 2011 and 2015. The average prevalence rate to be used here is 2.18 per 1000 patients. 19
This prevalence rate is based on estimates of electronic patients databases of general practitioners, and hence it can be regarded as the prevalence rate to be used in calculating n1. With respect to the prevalence
rate for physiotherapy visits no data were available in the literature. An approximation is derived from the reported treatments by the practice Fysiotherapy Buitenpost. The databases were searched for the code MDC 7120, the code to indicate treatment for tendinitis
16The authors reported 116 prevalent cases in the sample of
57,725 registered persons.
17107 incident cases over the year 2009.
18Counts were initially made in person-years; the overall
practice population counted 10,651 person years.
19The average PR rate calculated as:
P RG =
2.01 + 2.35
2 (11)
leg/foot. 20 The reported number of patients treated
under MDC 7120 was 6. On average, patients visit the practice 5.3 times for treatment per case. Difficult is that physioterapy practices do not have a more or less fixed number of patients as do general practitioners or health insurance companies. The total number of physiotherapy practices in the Netherlands for 2015 were estimated at 4,700. 21 According to the Dutch bureau of statistics (CBS), total number of inhabitants of the Netherlands in 2015 were 16,900,726 individuals.
22 This means that each practice will serve on average
3596 persons of the total Dutch population. 23
Assuming Fysiotherapy Buitenpost is representative for the average practice, the approximate prevalence rate for the physiotherapy population is 1.67 per 1000.
24
With regard to the prevalence rate for hospital services, data provided by a large Dutch health insurer have been used. With regard to medical specialist health products, there are two codes that can be used to indicate a diagnosis of Achilles tendon surgeries (Table 2). From the data however cannot be derived what the exact Achilles problem treated was. These data might hence also include for example surgical interventions regarding Achilles tendon ruptures.
Medical Specialism Code Description
General Surgery 262 Achilles tendon
Orthopedics 3403 Achilles tendon
TABLE 2: Diagnosis codes medical specialist care health insurers
Since the cost declaration procedures for the years 2015 and even 2014 have not yet been closed, the data for those years are incomplete and cannot be regarded reliable estimates. Therefore the total number of surgical Achilles treatments for the year 2013 has been chosen, since for that year the procedure has been finalised. The total number of insured for the year 2013 for the specific health insurer were 544,483. The total number of reported cases for general surgery are 163, and for orthopedics 73. This makes a total of 236 cases
20Note here that the code resembles a tendinitis, which is not
one to one equal to tendinopathy.
21Estimations by Rabobank and ABN Amro in reports
evalu-ating the physiotherapy environment in the Netherlands, reported on-line: www.rabobankcijfersentrends.nl and www.abnamro.nl.
22statline.cbs.nl/statweb/publication 23 = 16, 900, 726 4700 (12) = 3596 24 P RP = 6 3.596 (13) = 1.67
for 2013. This total indicates a prevalence rate of 0.43 per 1000 persons for the sample of insured. 25 Table
3 summarises all approximated prevalence rates for the three care providers.
Health care provider Prevalence Rate
General Practitioner 2.18
Physiotherapist 1.67
Hospital 0.43
TABLE 3: Prevalence rates Achilles tendinopathy per health care provider
4.1.2. Disability Weights
As discussed in section 2.5.3, disability weights specifically for Achilles tendinopathy have not yet been established. Since the weights have been provided for musculoskeletal disorders with respect to the leg region for three varying degrees - mild, moderate and severe [51] - those data will be used as approximation for disability weights for Achilles tendinopathy. This approach seems justified since Achilles tendinopathy is a musculoskeletal disorder in the leg area. However, it is not clear in which of the categories the injury should fall. Therefore two DALY calculations will be performed using both the lowest weight (mild) and the highest weight (severe) in order to indicate the range in which the number of DALYs for Achilles tendinopathy will likely fall.
The use of the VISA-A score has been rejected for broadly two main reasons. Firstly because the formula for DALY calculation is explicitly designed for the use of disability weights. Second of all, if we were to regard the VISA-A score as a quality adjusted life weight, according to Sassi (2006) [52] the disability weights could be calculated from D = 1 − Q. This latter holds only if it is initially assumed that the level of disability indicated by the disability weights is equivalent to the loss of quality of life indicted by the quality of life weight. It is however nowhere proven that the VISA-A score can be regarded as this equivalent to the quality weight. The following calculations shed some doubt on the validity of the measure as disability weight. When the VISA-A score would be taken as instrument for quality of life weights (first rescaling with a factor 100 to fit the 0 - 1 scaling of the quality weights), the equivalent weights for pre-surgical patients would be 0.61 expressed in quality weight. 26 The corresponding
disability weight would then be 0.39. Compared to the disability weights for severe musculoskeletal leg injuries, this figure seems unreasonably large. The VISA-A
25
P RH =
236
544.483 (14)
= 0.43
Source type Reported Duration
Fysioinfo.com Accute 6-10 weeks
Fysioinfo.com chronic non-surgical 3-6 months
Sportgeneeskunde.com post-surgical recovery 4-12 months
Roos et al., 2004 [50] chronic 5.5 months
patient.info N\A 3-6 months
De Jong et al., 2011 [16] chronic pre-trial 62.5 weeks
Lebrun 2008 [32] chronic 11 months
TABLE 4: Indicated durations Achilles tendinopathy per source
derived disability weight appears to be 2.3 times as large as severe MSK leg injuries, and a staggering 17 times larger than the mild MSK leg injury disability weight. Although an instrument to measure severity of Achilles tendinopathy is very welcome, the functioning of the VISA-A score in enabling quantitative research as is posed by Robinson (2001) [49] may be restricted to quantifying clinical treatment effects.
4.1.3. Duration
Whereas the duration of tendinopathy seems one of the most straightforward variables to quantify, in practice this seems somewhat more complicated. No scientific information could be found regarding an estimate of the mean duration of symptoms.
Complications in stating a mean duration are most likely caused by the fact that Achilles tendinopathy is a degenerating process. The injury tends to get worse, and the complaints more severe as a patient continues to overuse the tendon. Then differences in recovery tend to vary with treatment type as well. Surgical interventions are typically only committed to if conservative non-surgical treatment has failed [46]. Therefore duration until recovery for patients in need of surgery are the sum of maximum duration until recovery of non-surgical patients, and the recovery time of the surgery. The mean recovery time from surgery might differ from one type of operation to another. Using table 4, a lower boundary will be set at 6 weeks and an upper boundary at 18 months. 27 Computation of averages cannot be
justified since the different cases cannot be weighted. The indicated range of values will hence be used in the calculation of the range of DALYs.
4.2. Data for Monetary Valuation
In order to estimate the direct medical costs associated with Achilles tendinopathy (equation (10)), estimates of average prices for medical services per care provider need to be approximated. For the number of prevalent cases the prevalence rates as summarised in table 3 will be used.
27the sum of max non-surgical duration (6 months) and max
post-surgical recovery time (12 months).
4.2.1. Approximation of Care Prices
Zorginstituut Nederland provides a list of specific monetary reference prices for a range of care products and services per care provider. It is however not entirely clear how the reference prices have exactly been computed since the calculations have not been provided. The reference prices seem to differ from prices charged by the different care providers. For instance, the Dutch Health Authorities (Nederlandse Zorg Autoriteit) reports the 2015 prices for a standard visit at the general practitioner at e9.04. The guidelines however pose an amount per standard visit of e33. However unclear how derived specifically, in order to allow for the aim of uniformity and comparability, here the reference prices will be used in the calculations. For physiotherapy care, establishing prices is somewhat more complicated, since different prices are used for different visits. As such there are prices for (among others) intake visits, individual sessions and group sessions. With respect to physiotherapy visits, again the reference prices will be used. Standard prices per visit are expected to provide reasonable estimates here, since for these two care providers prices per session or visit do not vary per cause. A visit (consult) at the GP costs the same non-regarding the disease. The only cost differences arise from pharmaceutical prescriptions or services performed (e.g. stitching or bandaging). Those services will be separately charged per visit. With respect to Achilles tendinopathy there are no specific prescriptions or additional services generally provided. The same reasoning applies to the physiotherapy sessions.
Code Description Care Product Total Number of cases Average Prices General Surgery
199299012 Visit polyclinic; non-specified injury 40 e506.40
199299013 Maximum 5 days nursing days 1 e2120.55
199299016 More than two visits polyclinic 3 e320.94
199299028 Consult polyclinic 44 e234.24
199299059 Surgery non-specified injury 39 e1808.31
199299060 Surgery (incl. nursing) non-specified injury 35 e2990.88
199299084 Knee surgery non-specified injury 1 e2889.71
Total 163 e1299.02
Orthopedics
199299012 Visit polyclinic; non-specified injury 25 e514.36
199299013 Maximum 5 days nursing days 0
-199299016 More than two visits polyclinic 2 e468.88
199299028 Consult polyclinic 23 e200.38
199299057 Surgery non-specified injury 2 e2271.60
199299058 Surgery (incl. nursing) non-specified injury 1 e4267.40
199299059 Surgery non-specified injury 5 e2033.24
199299060 Surgery (incl. nursing) non-specified injury 15 e2768.38
Total 73 e1080.96
Total 236 e1231.57
TABLE 5: Prices of specialist care products with diagnosis 262 and 3403
by De Friesland are provided in table 5.
In the column Average Prices prices per code and care product have been reported in 2013 prices. The prices listed as totals are computed as weighted av-erages. From the table can be already inferred that some of the declarations bearing the Achilles tendon description are not at all Achilles tendon related. For instance code 199299084 corresponds to a knee surgery. Since surgery specifics cannot be inferred from the label non-specified injury it might also be that the reported surgeries have been conducted with regard to different Achilles tendon injuries, for instance Achilles tendon ruptures. According to the health insurer the reported data are however the payments made with inclusion of the coding for Achilles tendinopathy (Achillespeesontsteking). Since it is not clear whether the mistake was here to code a knee-surgery instead of a tendon-surgery, or to code with Achilles tendon injury instead of knee injury, the observation is not removed but kept in calculating the average.
Care Provider Price Year
CG e33 2014
CP e174.90 2014
CH e1231.57 2013
TABLE 6: Average prices per case per care provider Table 6 summarises the average prices for CG, CP,
and CH per case. Since from data of Fysiotherapy
Buitenpost was derived that the average patient receiving treatment for Achilles tendinopathy visited
5.3 times, average costs of one visit are multiplied by a factor 5.3 to resemble average costs per case.
4.2.2. Consumer Price Index
The prices reported in table 6 are mentioned in nominal prices of the year they occured. In order to calculate the 2015 equivalent, they will have to be expressed in 2015 prices using the consumer price index (CPI). The CPI is reported by the Dutch CBS. The base year of calculations is 2015. As such the CPI for 2015 is 100.00. The corresponding CPIs for 2013 and 2014 are 98.44 and 99.40 respectively. Table 7 presents the average prices per case per care provider in 2015 prices using these CPIs.
Care provider 2015 price
CG e33.20
CP e175.96
CH e1251.09
TABLE 7: Average prices per case per care provider 2015 prices
4.2.3. Productivity Loss
guidelines only concrete data for measuring absenteeism related productivity costs have been provided. These data provided will however not yet enable a researcher to fully determine absenteeism related costs due to a specific disease. For an accurate measurement the amount of hours absent due to specifically that disease under consideration would still need to be established. These required disease specific data or related information are provided.
What is more, there are no guidelines as to indicate how to measure presenteeism loss. Briefly it is recommended that the researcher uses a standardised questionnaire in order to measure such presenteeism related productivity losses.
In existing research no values for productivity loss due to Achilles tendinopathy have been reported. More-over, approximations regarding presenteeism scores or productivity losses have not even been reported related to the overall group of Musculoskeletal disorders or other types of comparable diseases.
The extent to which worker productivity will fall due to disease is likely to depend on the severity of that condition [11]. For Achilles tendinopathy not even average severity in terms of pain and duration could be derived with certainty. Since estimates for presenteeism or absenteeism scores attributable to either Achilles tendinopathy or any comparable disease are not available, productivity losses 28 will not be
estimated.
5. RESULTS
5.1. DALYs
This section presents a range of values in which the true DALY burden is likely to fall. The lower boundary values have been chosen as described in the Data section. The overall prevalence rate has been chosen to be the P RG rate, for that figure will best approximate
the total number of inhabitants suffering from Achilles tendinopathy regardless of the treatments received.
DALYL = Np× DWL× TL (15) Np= 16, 900.726 × 2.18 = 36, 843.58 DWL = 0.023 TL = 6 52 DALYL = 97.78 (16)
Where the subscript L indicates that for the
variables their respective lower bound values have been computed.
28Productivity losses of both paid and non-paid work, I tand Ht, equations (5) and (6). DALYH= Np× DWH× TH (17) Np= 36, 843.58 DWH= 0.171 TH= 18 12 DALYH= 9, 450.38 (18)
Where the subscriptHindicates that for the variables
their higher bound values has been substituted. 5.2. Direct Medical Costs
This section presents an estimation of the direct medical costs arising from various types of treatments of Achilles tendinopathy. Since the data collected for estimation of surgical costs are feared to be somewhat biased due to misreporting, the estimated direct costs are expected to overestimate the real monetary costs, mainly since in the surgical data inclusion of Achilles rupture data are feared. Combining the data presented in tables 3 and 7, the monetary costs of direct medical services are estimated as follows29 30:
Dt= n1CG+ n2CP+ n3(CH+ CG)
= 15, 522, 875.72 (21)
6. DISCUSSION
When analysing the results of section 5.1 we see that the lower bound and the upper bound of DALY values differ to a great extent. This represents the fact that the values needed for estimation could not be precisely determined. The corresponding range therefore lacks the same degree of conciseness. In order to put the computed DALY values in perspective, and to determine the relative burdens of the estimates (for both the lower- and upper bound values) we want to compare the findings with values reported for overall DALY burden and total burden for MSK diseases in the Netherlands as reported in the Global Health
