University of Groningen
The Severity of Anaphylactic and Systemic Allergic Reactions
Pettersson, Maria Eleonore
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The Severity of Anaphylactic and
Systemic Allergic Reactions
The author gratefully acknowledges the financial contributions for the printing of this thesis:
Groningen University Institute for Drug Exploration (GUIDE) University Medical Center Groningen (UMCG)
University of Groningen
Lay-out and print by: ProefschriftMaken // www.proefschriftmaken.nl ISBN, printed version: 978-94-034-0558-2
ISBN, electronic version: 978-94-034-0559-9 Copyright © by M.E. Pettersson, 2018
The Severity of Anaphylactic and
Systemic Allergic Reactions
PhD Thesis
to obtain the degree of PhD at the University of Groningen
on the authority of the Rector Magnificus Prof. E. Sterken
and in accordance with the decision by the College of Deans. This thesis will be defended in public on
Monday 18 June 2018 at 16.15 hours
By
Maria Eleonore Pettersson
born on 16 June 1988 in Badelunda, Sweden
Supervisors Prof. A.E.J. Dubois Prof. G.H. Koppelman Assessment committee Prof. D.S. Postma
Prof. A.C. Knulst Prof. G.C. Roberts
CONTENTS
Chapter 1 - General introduction 9
Chapter 2 - Is 30 minutes between doses long enough in oral food challenges? 25 Chapter 3 - Prediction of the severity of allergic reactions to foods 33 Chapter 4 - Greater severity of peanut challenge reactions using a high fat versus
low fat matrix vehicle
55
Chapter 5 - Clinical reactivity to individual tree nuts and peanut differs among the sensitized pediatric population
63
Chapter 6 - Apolipoprotein B: a possible new biomarker for anaphylaxis 77 Chapter 7 - Association of STAT6 gene variants with food allergy diagnosed by
double-blind placebo-controlled food challenges
85
Chapter 8 - Mastocytosis and age, but not baseline tryptase, specific IgE or total IgE, independently determine the severity of systemic reactions to yellow jacket stings.
95
Chapter 9 - Summary and general discussion 113 Appendices - Nederlandse samenvatting - Svensk sammanfattning - Biography 127 129 133 141
ABBREVIATIONS AF - allele frequency ApoB - apolipoprotein B BAT - basophil activation test bsT - baseline serum tryptase CD - cumulative dose CI - confidence interval CMA - cow’s milk allergy
DBPCFC - double-blind, placebo-controlled food challenge ED - eliciting dose
eQTL - expression quantitative trait loci FBAT - family based association test ISM - indolent systemic mastocytosis MH - methylhistamine
MI - myocardial infarction
MIMA - methylimidazole acetic acid OFC - oral food challenge
PAF - platelet-activating factor
PAF-AH - platelet-activating factor, acetylhydrolase sIgE - specific immunoglobulin E
SNP - single nucleotide polymorphisms SPT - skin prick test
STAT6 - signal transducer and activator of transcription 6 UMCG - University Medical Center Groningen
UP - urticaria pigmentosa YJV - yellow jacket venom
CHAPTER 1
1
When inquiring about the beliefs of the general public regarding allergies, several common misconceptions seems to exist. The word “allergy” is frequently incorrectly used as a syn-onym for all symptoms occurring after an insect sting, ingestion of a culprit food, or related to medication use. Moreover, the general public frequently confuses non-allergic food reac-tions, such as food intolerances, with food allergies, which can result in an unfounded belief that food allergy is less severe than it truly is. However, what does it really mean?
1.1 AllERgy dEfINITIONS
An abnormally strong response to a certain substance resulting in symptoms or signs, which is tolerated by the majority of the population, is known as hypersensitivity. (1) Allergy is defined by the European Academy of Allergology and Clinical Immunology as a hypersensitivity reaction initiated by immunological mechanisms. (1) Allergy frequently arises in the first few months of life, but it can develop at any age. The term allergy is broadly used but generally includes a set of clinical symptoms elicited by immunologic mechanisms, that may be mediated by immunoglobulin and/or through cell-mediated responses. These responses are frequently mediated by Immunoglobulin E (IgE) and these individuals are generally referred to as having an IgE-mediated allergy. (1) Many allergic diseases have a chronic course, however there are ways to treat and manage them and some patients may outgrow their allergies completely, even if severe. (2)
Allergic reactions are elicited by allergens. Most allergens are glycoproteins which cause the allergic response by reacting with the immune system. Allergens may be airborne, such as grass pollen, tree pollen or mite; ingested, as in the case of food allergens; or transferred by stinging insects, for instance yellow jacket, wasp or bee. Another group of allergens are medications, with certain types of antibiotics as common elicitors. (3) The generation of specific IgE (sIgE) after exposure to an allergen is known as sensitization. (4) However, sensitization without the development of symptoms after allergen exposure, also known as asymptomatic sensitization, is common. Thus, an sIgE mediated allergy re-quires both the development of symptoms after exposure to an allergen and the presence of sensitization. (5)
Cross-reactivity may occur when an allergen of similar structure to the original sensitizing al-lergen crosslinks with an antibody and elicits an immunologic response. For example, a birch tree pollen allergen shares structural similarities with a specific hazelnut allergen, which may lead to clinical reactivity to hazelnut in patients sensitized to birch tree pollen. (6)
Atopy is defined as an individual and/or a familiar tendency to become sensitized and produce IgE antibodies in response to exposure of allergens commonly occurring in the environment. Allergic asthma, atopic dermatitis, allergic rhinoconjunctivitis, food allergy and IgE mediated anaphylaxis are examples of clinical disorders considered to fall under the definition of atopic diseases. (1)
1.2 ANAphylAxIS Defining anaphylaxis
Anaphylaxis is defined as a “severe, life-threatening generalized or systemic hypersensitiv-ity reaction”. (1) Anaphylaxis may be mediated by sIgE but alternative mechanisms have also been suggested. (5) An anaphylactic reaction is rapid in onset, varying from minutes to a few hours, and frequently includes multiple organ systems. The skin and mucous membranes are frequently involved, with symptoms and signs such as itching, angio-edema, flushing and hives. Gastrointestinal, respiratory and cardiovascular symptoms are also common, however signs of shock is not always present, even in fatal reactions. (7) The overall fatality rate for anaphylaxis is low, under 0.001%. (8) The clinical criteria for diagnosing anaphylaxis, as defined by Sampson et al. (9), are shown in Table 1.
Table 1. The clinical criteria for diagnosing anaphylaxis, as defined by Sampson et al (9). One out
of the three criteria needs to be fulfilled to receive the diagnosis of anaphylaxis.
Clinical criteria of Anaphylaxis
1. Acute onset of symptoms or signs, with involvement of:
• Skin or mucosa (for example hives; generalized itch, flush or erythema; angioedema) AND one of the following:
• Reduced blood pressure (BP) or related symptoms (for example syncope) • Airway compromise(for example wheeze, bronchospasm, dyspnea, reduced peak
expiratory flow rate (PEFR))
2. Two or more of the following symptoms after exposure to a confirmed allergen for that patient: • History of severe allergic reaction
• Skin or mucosa (for example hives; generalized itch, flush or erythema; angioedema) • Airway compromise (for example wheeze, bronchospasm, dyspnea, reduced PEFR) • Reduced BP or related symptoms (for example syncope)
• In food allergy: gastrointestinal symptoms (for example vomiting, abdominal pain, diarrhea )
3. Hypotension after exposure to a confirmed allergen for that patient.
• Infants and children: >30% drop in systolic BP or age specific low systolic BP; <70 mmHg in 1 month-1 year olds, <(70 mmHg +(2xage)) in 1-10 year olds, <90 mmHg in 11-17 year olds.
1 Epidemiology
Anaphylaxis is frequently elicited by foods, medications or stinging insect venoms, but it could also be triggered by an unidentified cause. The distribution of the causes varies with geographic location and the age of patients. Generally, foods and drugs are the most common triggers of anaphylaxis in patients presenting to the emergency department. (8) Foods are the most common elicitor for anaphylaxis in children, while anaphylaxis caused by drugs and stinging insect venom is more common in adults. (8)
Certain external factors, so-called cofactors or augmentation factors, have also been shown to influence allergic reactions. These include the use of certain medications, in particular nonsteroidal anti-inflammatory drugs (NSAIDs); alcohol; exercise; concomitant disease; acute infection; premenstrual status in females and mast cell diseases. (10-12) Treatment
Initial treatment of anaphylaxis consists of an intramuscular injection of adrenaline in the mid-outer thigh, and placing the patient in a supine position with the lower extremi-ties elevated. If there is respiratory distress or vomiting, a position of comfort might be preferred. If indicated, supplemental oxygen, intravenous fluid resuscitation and cardio-pulmonary resuscitation should be provided. Antihistamines, glucocorticoids and beta-2 adrenergic agonists should not be used as monotherapy or administered before treatment with adrenaline. Patients not responding to repeated dosages of adrenaline, supplemental oxygen and intravenous fluid resuscitation require intensive care treatment. (13)
Management and prevention of recurrence
Patients with previous anaphylactic reactions should be evaluated by a specialist, receive optimal treatment of additional atopic disease and be given information how to man-age and prevent recurrences. The patient should be prescribed one or more adrenaline auto-injectors, which must be carried consistently and used if anaphylaxis reoccurs. Avoid-ance of confirmed triggers and allergen specific immunotherapy should be initiated, if applicable. (13)
1.3 fOOd AllERgy
General introduction to food allergy
Food allergy has been defined as an adverse reaction to food, which is reproducible on each contact with the culprit food and mediated by an immunologic mechanism. The clinical symptoms of food allergy involves the skin, gastrointestinal, respiratory and
car-diovascular tracts. (14) Reactions to foods is most commonly triggered by ingestion, but may also rarely occur after inhalation or skin contact. (13)
A thorough clinical history is vital to the diagnosis of food allergy, as it can ascertain the probability of the diagnosis, identify the potential elicitor and suggest the immunological mechanism involved. The clinical evaluation should involve associated atopic disease, such as asthma, atopic dermatitis and allergic rhinoconjunctivitis. Skin prick tests (SPT) and measurement of the level of food-specific IgE (sIgE) are first-line tests to evaluate IgE sensitization. (14) However, asymptomatic sensitization is frequent and these tests in combination with a careful clinical history frequently over-estimate the diagnosis of food allergy. (15-17) Therefore, oral food challenges (OFC) are usually required to make the diagnosis.
The double-blind, placebo controlled food challenge (DBPCFC) is the gold standard test for the diagnosis of food allergy. In this test the patient receives either the placebo or active food on two separate days in random order. The food used during the placebo and active day of the DBPCFC should be indistinguishable from each other in terms of sensory properties. (18)
In order to prevent severe reactions during the test, patients receive the food in increasing dose increments, with a set time-interval between doses. The food challenge is stopped if a clear clinical allergic reaction is observed or if the last dose is ingested without the development of a clinical reaction. Even though life-threatening reactions are rare, staff performing OFCs should be trained and equipped to treat potentially severe allergic reac-tions and anaphylaxis. (18)
The management of food allergy is divided into short-term and long-term intervention strategies. The short-term interventions are directed at the treatment of acute allergic reactions, such as injection of intra-muscular adrenaline for anaphylaxis. The long-term strategies are employed to minimize the risk of further reactions. This is achieved through patient education, dietary adjustment and prescription of adrenaline auto-injectors, if indicated. (19)
The dietary adjustment should eliminate the culprit food. Patients should be re-evaluated at regular intervals to examine whether they have developed tolerance to the food in question, as unnecessary dietary elimination impairs quality of life and extensive dietary elimination can lead to nutritional deficiencies. (19)
1
Currently, there is growing interest in immune-modulating treatment options for food allergy, such as sublingual and oral immunotherapy to induce tolerance. However, these are currently not recommended outside of the research setting due to the potential for severe adverse events. (19)
Identifying patients at risk for severe reactions is important for accurate management and targeted prescription of adrenaline auto-injectors. However, accurate identification of these patients is currently not possible, which results in a great deal of uncertainty for patients, caregivers and clinicians.
Scoring of severe food allergic reactions
Various scoring systems for determination of the severity of food allergic reactions have been developed. However, currently there is no consensus among clinicians and research-ers on which scoring system to use. The use of a particular scoring system diffresearch-ers per center according to own preferences, research applicability and clinical experience. Risk factors and co-factors for the severity of food allergic reactions
A correct assessment of the risk of severe food allergic reactions is important for the successful management of patients. Several risk factors have been proposed, however the impact of each factor in the development of severe reactions is unknown. Patients with previous anaphylaxis to food or severe asthma have a higher risk of severe reactions compared to other patients. (20, 21) Moreover, the age of the patients also seems to have an influence on the severity of reactions, with adolescents and young adults generally having the most severe food allergic reactions. (8)
Food allergic reactions do not seem to show a clear dose-response relationship between the ingested dose and the severity of the ensuing reaction. Threshold doses required to initiate an allergic reaction vary between patients, and do not remain stable over time in some food allergic patients. (22) In a unique study, where the food challenge procedure was allowed to continue with additional doses after the initial reaction, many, but not all patients had allergic reactions which progressed to anaphylaxis. (23) It has previously been suggested that dose sensitive patients have more severe allergic reactions, however this has not yet been shown in published research. (24-26) Thus, the precise relationship between dose and the development of severe reactions is currently unclear.
Biomarkers
There are few published studies examining biomarkers for severe food allergic reactions. Currently, there is no biomarker available which accurately can predict severe food allergic reactions in all patients.
Levels of sIgE and SPT wheals to certain foods have been shown to weakly correlate with severe reactions and cut-off values have been developed to make recommendations on when oral food challenge testing is redundant. (27-29) Thus, these cut-offs are more appropriate for predicting clinical reactivity as compared to asymptomatic sensitization. However, they are not clinically useful for prediction of severe reactions in a food allergic population.
In component-resolved diagnostic tests (CRD), sIgE antibodies are measured against indi-vidual allergenic food proteins known as major allergens. This test was developed with the prospect to improve the specificity of sIgE testing. (30) The use of this technique has been broadly studied for peanut, and the allergen components Ara h 2 and Ara h 6 have been shown to be predictive markers for severe reactions to peanut. (31) However, geographi-cal differences in sensitizations patterns have been demonstrated for peanut allergy. (32) Moreover, the cut-off levels for these predictors are not applicable to the majority of the peanut allergic population and the impact of these results are controversial. (33) More large-scale studies are needed to confirm allergen components to be predictive of severe reactions for other types of food.
Currently, potential biomarkers for severe food allergic reactions such as basophil activa-tion tests (BATs), baseline serum tryptase (bsT) levels and platelet-activating factor (PAF) and/or PAF acetylhydrolase (PAF-AH) are limited to the research setting.
1.4 YEllow jackEt (VESpula SpEciES) VEnoM allERGY General introduction to Yellow jacket venom allergy
Vespid and honeybee stings are the most prevalent insect stings in central and northern Europe. Vespula are commonly known as yellow jackets in USA and wasps in Europe. Vespula preferably build their nests in attics, underground or other similar sheltered loca-tions. Only the queens survive the winter, thus larger populations are only seen in the summer and most insect stings occur during that season. (34)
Most venom allergens are glycoproteins and the major allergens in vespid venoms are phospholipase A1 (Ves v 1), hyaluronidase (Ves v 2) and antigen 5 (Ves v 5). (35-37) Some components of the venoms have toxic effects. Generally, toxic reactions are dependent on dose, influenced by the composition of the venom, and only occur after fifty to several hundred stings. (38-40) A single vespula sting releases between 1.7 to 3.1 μg of venom. (41) The venom composition of individual allergens have many similarities, thus cross-reactivity between different species of vespids is common. (42, 43)
1
Sting reactions can be classified into normal local reactions, large local reactions, systemic toxic reactions and systemic allergic reactions. Normal local sting reactions in non-allergic patients elicit symptoms of pain, erythema and mild swelling around the site of the sting. These symptoms usually fade after 24 hours, but may remain for a few days. (34) Large local reactions have been defined as a swelling larger than 10 centimeters, which persists for more than 24 hours, and rarely includes the presence of blisters. Large local reactions may last for days to weeks and involve eyes, lips or a whole limb. These reactions may also be accompanied by shivering, fever, headaches or general malaise. The pathogenesis of large local reactions is unknown. (34)
A prevalence of between 0.3 and 7.5% of systemic reactions to insect stings have been reported in Europe. (34) Venom sensitization is present in the majority of patients with previous systemic sting reactions. (44) Symptoms of the skin, gastrointestinal, cardiovas-cular and respiratory tract can occur. One of the most frequently used classifications of the severity of systemic reactions to insect stings was published by Mueller, see Table 2. (45) Symptoms usually develop within minutes after the sting, but can appear hours or rarely even days later. (46) Fatal reactions to insect stings occur, however the incidence is low, between 0.03 to 0.48 fatalities per 1.000.000 individuals a year. (47) However, between 40-85% of patients with fatal reactions to insect stings had no history of previous anaphy-lactic reactions. (48, 49)
Table 2. Classification of systemic reactions to insect stings according to Mueller. (45)
Grade I Generalized urticaria, itching, malaise and anxiety
Grade II Any of the above plus two of more of the following: angioedema, chest constriction, nausea, vomiting, diarrhea, abdominal pain, dizziness
Grade III Any of the above plus two or more of the following: dyspnea, wheezing, stridor, dysarthria, hoarseness, weakness, confusion, feeling of impending disaster
Grade IV Any of the above plus two or more of the following: fall in blood pressure, collapse, loss of consciousness, incontinence, cyanosis.
Diagnosis and treatment of Yellow jacket venom allergy
The diagnosis of Yellow jacket venom (YJV) allergy is based on a detailed clinical history of a systemic sting reaction, in addition to clinical sensitization as shown by detection of venom specific IgE in serum and/or a positive skin test. (34) The history is highly important in making a correct diagnosis, since asymptomatic venom sensitization is frequent. (50) All patients with a history of systemic reactions to YJV should carry adrenaline auto-injec-tors and be evaluated by an allergy specialist for the possibility of venom immunotherapy
(VIT). Subcutaneous VIT is an effective treatment which reduces the risk of additional sys-temic reactions, prevents fatal reactions and improves the quality of life of patients. (34) Risk factors for the severity of allergic reactions to Yellow jacket venom
In patients with a history of systemic sting reactions, a majority will experience a new systemic reaction after a subsequent sting. (51) The risk of developing a systemic sting re-action increases with a shorter time interval between subsequent stings. (52) Conversely, very frequent stings, more than 200 a year, seem to induce tolerance. (53, 54)
Children with a history of previous mild cutaneous reactions have been shown to have a 10% risk of recurrence of systemic reactions after an additional sting. (55) In adults this risk was 14-20% after a history of previous mild systemic reactions and 79% with a history of previous severe systemic reactions. (56, 57) Systemic sting reactions in children tend to be milder than in adults, and elderly patients generally develop more severe sting reac-tions. (58-60)
Several factors seems to be associated with severe systemic sting reactions. Cardiovascu-lar disease and treatment with beta-blockers or angiotensin-converting enzyme inhibitors have been suggested to be associated with such reactions. However reports describe conflicting results. (61) Patients diagnosed with indolent systemic mastocytosis (ISM) have clonal proliferation of abnormal mast cells and represent a particular risk group for frequent and severe anaphylactic reactions. This is likely to be caused by excessive mast cell mediator release following triggering of mast cells. (62) Moreover, patients with mas-tocytosis have been shown to have mainly severe or even fatal sting reactions in several case studies. (63, 64)
A strong relationship between reaction severity to insect venoms and elevated baseline serum tryptase (bsT) levels have been shown. The bsT level is thought to reflect the mast cell number and activity, considering that tryptase mainly is produced by mast cells. (65) Additionally, elevated bsT levels in patients without diagnosed mastocytosis have been shown to be associated with severe systemic sting reactions. (66)
1.5 aiM anD outlinE of thESiS
This thesis aims at investigating and exploring the multifactorial nature of the severity of systemic anaphylactic and allergic reactions from different perspectives. In this thesis we will explore a new possible biomarker, identify independent risk factors for the severity of systemic allergic and anaphylactic reactions and investigate the genetics of food allergy.
1
Special attention will be given to examine the relationship between the eliciting dose and the severity of reaction in food allergy.
In the first part of this thesis, we will address the severity of systemic allergic reactions to foods in a pediatric population. In Chapter 2, we will look at a potential challenge in di-agnosing food allergy when using the gold standard double-blind, placebo controlled oral food challenge (DBPCFC). This chapter examines whether the DBPCFC, with a 30 minute interval between doses, is safe in patients reporting longer time-intervals between inges-tion of the suspected food and the subsequent reacinges-tion. Independent factors relevant for the prediction of the severity of food allergic reactions and the relationship between the eliciting dose and severity of reaction will be addressed in Chapter 3. This chapter also examines the influence of using different scoring systems and the impact this can have on predicting the severity outcome. In Chapter 4 we investigate whether patients receiving a high fat matrix in DBPCFCs with peanut have differences in the severity of reaction or eliciting dose, compared to when a low-fat matrix is used. The differences in frequency of clinical reactivity and severity of reaction between peanut and tree nuts is presented in Chapter 5. In Chapter 6 we will investigate the association between a new possible bio-marker, apolipoprotein B-100, and the severity of food allergic systemic reactions. Chapter 7 examines a candidate gene for the presence and severity of food allergy, by investigating STAT6 gene variants in children with food allergy diagnosed by DBPCFCs.
In the second part of this thesis we will investigate the severity of systemic allergic reac-tions to yellow jacket stings in adults. In Chapter 8 we evaluate independent clinical risk factors for the severity of systemic allergic reactions to yellow jacket stings and quantify how much of these reactions may be predicted by the identified factors.
Finally, a summary of the main results of this thesis, general discussion and future per-spectives are provided in Chapter 9.
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33. Turner PJ, Baumert JL, Beyer K, Boyle RJ, Chan C-H, Clark AT et al. Can we identify patients at risk of life-threatening allergic reactions to food? Allergy 2016;71:1241-55 DOI: 10.1111/all.12924. 34. Biló BM, Rueff F, Mosbech H, Bonifazi F, Oude-Elberink JN; EAACI Interest Group on Insect Venom
Hypersensitivity. Diagnosis of Hymenoptera venom allergy. Allergy. 2005;60:1339-49.
35. King TP, Spangfort MD. Structure and biology of stinging insect venom allergens. Int Arch Allergy Immunol 2000; 123:99-106.
36. Hoffman DR, Jacobson RS. Allergens in Hymenoptera venom XII: How much protein is in a sting? Ann Allergy 1984;52:276-278.
37. King TP, Kochoumian L, Joslyn A. Wasp venom proteins: phospholipase A1 and B. Arch Biochem Biophys 1984;230:1-12.
38. Watemberg N, Weizman Z, Shahak E, Aviram M, Maor E. Fatal multiple organ failure following mas-sive hornet stings. J Toxicol Clin Toxicol 1995;33:471-4.
39. Sakhuja V, Bhalla A, Pereira BJ, Kapoor MM, Bhusnurmath SR, Chugh KS. Acute renal failure follow-ing multiple hornet stfollow-ings. Nephron 1988;49:319-21.
40. Kolecki P. Delayed toxic reaction following massive bee envenomation. Ann Emerg Med 1999; 33:114-6.
41. Hoffman DR, Jacobson RS. Allergens in Hymenoptera venom XII: How much protein is in a sting? Ann Allergy 1984;52:276-278.
42. Hoffman DR. Allergens in Hymenoptera venom. XXV: The amino acid sequences of antigen 5 mol-ecules and the structural basis of antigenic cross-reactivity. J Allergy Clin Immunol 1993; 92:707-16. 43. King TP, Lu G, Gonzales M, Qian N, Soldatova L. Yellow jacket venom allergens, hyaluronidase and phospholipase. Sequence similarity and antigenic cross-reactivity with hornet and wasp homologs and possible implications for clinical allergy. J Allergy Clin Immunol 1996;98:588-600.
44. Fricker M, Helbling A, Schwartz L, Müller U. Hymenoptera sting anaphylaxis and urticaria pigmen-tosa: clinical findings and results of venom immunotherapy in ten patients. J Allergy Clin Immunol 1997;100:11-5.
45. Mueller HL. Diagnosis and treatment of insect sensitivity. J Asthma Res 1966;3 :331-333. 46. Müller UR. Insect Sting Allergy 1990. Gustav Fischer, Stuttgart.
47. Antonicelli A, Bilò MB, Bonifazi F. Epidemiology of Hymenoptera allergy. Curr Opin Allergy Clin Im-munol 2002;2:1-6.
48. Mosbech H. Death caused by wasp and bee stings in Denmark 1960-1980. Allergy 1983;38:195-200. 49. Sasvari T, Müller U. Fatalities from insect stings in Switzerland 1978 to 1987. Schweiz Med
Wochen-schr. 1994;124:1887-94.
50. Fernandez J, Soriano V, Mayorga L, Mayor M. Natural history of Hymenoptera venom allergy in Eastern Spain. Clin Exp Allergy. 2005;35:179-85.
51. Brown S, Wiese M, Blackman K, Heddle R. Ant venom immunotherapy: A double blind, placebo-controlled cross-over trial. Lancet 2003;361: 1001-1006.
1 52. Pucci S, Antonicelli L, Bilò MB, Garritani MS, Bonifazi F. The short interval between two stings as a
risk factor for developing hymenoptera venom allergy. Allergy 1994;49:894-6.
53. Bousquet J, Menardo JL, Aznar R, Robinet-Levy M, Francois-Bernard M. Clinical and immunologic survey in beekeepers in relation to their sensitization. J Allergy Clin Immunol. 1984;73:332-40. 54. de la Torre-Morin F, Garcia-Robaina JC, Vazquez-Moncholi C, Fierro J, Bonnet-Moreno C.
Epidemiol-ogy of allergic reactions in beekeepers: a lower prevalence in subjects with more than 5 years exposure. Allergol Immunopathol (Madr) 1995; 23:127-32.
55. Schuberth KC, Lichtenstein LM, Kagey-Sobotka A, Szklo M, Kwiterovich KA, Valentine MD. Epidemio-logic study of insect allergy in children. II. Effect of accidental stings in allergic children. J Pediatr 1983;102:361-5.
56. Engel T, Heinig JH, Weeke ER. Prognosis of patients reacting with urticaria to insect sting. Results of an in-hospital sting challenge. Allergy 1988;43:289-93.
57. Reisman RE. Natural history of insect sting allergy: relationship of severity of symptoms of initial sting anaphylaxis to re-sting reactions. J Allergy Clin Immunol 1992;90:335-9.
58. Chipps BE, Valentine MD, Kagey-Sobotka A, Schuberth KC, Lichtenstein LM. Diagnosis and treat-ment of anaphylactic reactions to Hymenoptera stings in children. J Pediatr 1980;97:177-84. 59. Lockey RF, Turkeltaub PC, Baird-Warren IA, Olive CA, Olive ES, Peppe BC, Bukantz SC. The
Hyme-noptera venom study I, 1979-1982: demographics and history-sting data. J Allergy Clin Immunol 1988;82:370-81.
60. Lantner R, Reisman RE. Clinical and immunologic features and subsequent course of patients with severe insect-sting anaphylaxis. J Allergy Clin Immunol. 1989;84:900-6.
61. Stoevesandt J, Hosp C, Kerstan A, Trautmann A. Hymenoptera venom immunotherapy while maintaining cardiovascular medication: safe and effective. Ann Allergy Asthma Immunol. 2015 May;114(5):411-6. doi: 10.1016/j.anai.2015.03.001.
62. Horny HP, Sotlar K, Valent P. Mastocytosis: state of the art. Pathobiology 2007;74:121-32. 63. Oude Elberink JN, de Monchy JG, Kors JW, van Doormaal JJ, Dubois AE. Fatal anaphylaxis after a
yellow jacket sting, despite venom immunotherapy, in two patients with mastocytosis. J Allergy Clin Immunol. 1997;99:153-4.
64. Biedermann T, Ruëff F, Sander CA, Przybilla B. Mastocytosis associated with severe wasp sting anaphylaxis detected by elevated serum mast cell tryptase levels. Br J Dermatol 1999;14:1110-2. 65. Schwartz LB. Clinical utility of tryptase levels in systemic mastocytosis and associated hematologic
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66. Haeberli G, Bronnimann M, Hunziker T, Müller U. Elevated basal serum tryptase and hymenoptera venom allergy: relation to severity of sting reactions and to safety and efficacy of venom immuno-therapy. Clin Exp Allergy 2003;33:1216-20.
CHAPTER 2
I
s30
mINUTEsbETwEENDOsEsLONGENOUGhINORALfOODChALLENGEs?
M. Eleonore Pettersson Bertine MJ. Flokstra- de Blok Sicco van der Heide
Jeanet Kukler Anthony EJ. Dubois
ABSTRACT
It is currently unknown whether the interval between doses in the double-blind, placebo-controlled food challenge (DBPCFC) is long enough to avoid accumulation of doses and the occurrence of potentially more severe reactions. The objective of this study was to investigate if patients who report longer time intervals (≥30 minutes) between ingestion of the allergen and the subsequent reaction, react to higher doses and have more severe reactions in the DBPCFC than patients with more rapid reactions (<30 minutes). The re-sults of this study showed that patients reporting longer time intervals between ingestion and reaction had a higher dose in the DBPCFC than those reporting more rapid reactions. (Eliciting dose: U=2531.5, P=0.004 Cumulative dose: U=2561.5, P=0.005) However, they did not experience more severe reactions (U=3149.0, P=0.214). An interval of 30 minutes between doses is thus long enough to allow for the DBPCFC to be performed safely in all patients, including those who may react to accumulated doses.
2 intRoDuction
To the Editor,
In clinical practice, the double-blind, placebo-controlled food challenge (DBPCFC) is consid-ered the gold standard for diagnosing food allergy (1). This test is performed with gradual increases in the dose of the culprit food at regular time intervals to reduce the adverse events. When performing the DBPCFC, an interval of 30 minutes is often used between the doses(1,2). However, it is currently unknown whether this interval is long enough to avoid reactions to accumulated doses, which might be more severe than reactions to individual doses.
The objective of this study was to investigate if an accumulation of doses in the DBPCFC occurs in patients who report longer time intervals (≥30 min) between ingestion of the culprit food and the subsequent reaction, as these patients could receive a subsequent dose before having reacted to the previous dose. This was done by dividing patients into two groups based on reaction time and comparing the eliciting dose (ED) and the cumula-tive dose (CD) as well as the severity of the challenge reaction, corrected for confounders for these outcomes. As patients with longer reaction times by history (≥30 min) might be expected to accumulate doses during challenge testing, they could have higher EDs and CDs as well as more severe reactions than those with shorter reaction times (<30 min). METhOdS
A database analysis of positive DBPCFCs (2002–2011), performed at University Medical Center Groningen was carried out. Children were challenged as a part of routine care for sus-pected food allergy. Unstable comorbidity or unwillingness to undergo the test were the only reasons to forego challenge testing, which was the case in <2% of the individuals. No children were excluded because of a history of previous anaphylaxis. Challenges were excluded from the present analysis when multiple food challenges to the same food were performed; in which case only the first challenge to each food was included (90 cases excluded). Patients were also excluded when there was no medical history for the tested food (103 cases) or if there was incomplete data for the relevant variables (92 cases). The exclusion of patients with only subjective symptoms in the DBPCFC (28 cases) had no influence on the outcome. Results from the five most commonly challenged foods were used for the analysis: milk, egg, peanut, hazelnut, and cashew nut. The DBPCFCs were performed according to previ-ously published procedures and protocols (2, 3). In brief, a food matrix was used to mask the suspected allergenic food. Administration of placebo and allergenic food using an
incremental, ‘semi-logarithmic’ scale occurred on separate days, at least a week apart, in random order. Double blinding was maintained until 48 h after the second test day. A food challenge was considered positive when objective symptoms occurred on the allergenic food-test day but not on the placebo day (2–5).
A scoring system was used to determine the severity of the allergic reaction during the oral challenge test6. The patients’ symptoms were allocated to different categories and received a corresponding score. The categories used and their score were the following: skin (1), upper airways (3), lower airways (3), gastrointestinal (2) and cardiovascular/ neurological symptoms (3). The scores of each category were summed and expressed as a severity index. The severity index ranges from 0–12 and is divided into groups. Scores from 0–2 are considered mild reactions. A score of 3–6 is regarded as a moderate reaction. The third group with scores of 7–12 is classified as severe reactions.
The statistical analysis of the data was performed using the statistics software package SPSS Statistics 17.0 for Windows. Reaction severity, ED, and CD were compared in patients with long (≥30 min) and short (<30 min) reaction times by history using the Mann–Whit-ney U-test. Possible confounders to the analysis were pre-selected through Spearman’s correlation test and multiple linear regression analysis by adopting a liberal p-value cut off (>0.2). Confounders reported in other studies were also included as well as biologi-cally plausible confounders and general demographics (age, sex). Subsequently, multiple linear regression analysis was used to assess any confounding by evaluating whether the coefficient of the association between reaction time and the outcomes changed by >10% by adding a possible confounder to the basic model. Factors tested and excluded as con-founders in the analysis were sex, age, type of allergenic food, history of asthma, history of atopic dermatitis, history of rhinoconjunctivitis, specific IgE level, and severity of the reaction following accidental ingestion by history.
RESultS
Two hundred and thirty-two cases were used for the final analysis. The age of the children ranged from 0.7 to 17.8 years, with a median of 5.8 years. Of the children, 56.9% were male and 43.1% were female. The DBPCFC were performed with peanut (34.1%), milk (27.2%), cashew nut (17.2%), egg (11.6%), and hazelnut (9.9%). For further demographics see Table 1. Patients reporting longer time intervals between ingestion and reaction (≥30 min) had a higher ED and CD in the DBPCFC than those reporting shorter time intervals between ingestion and reaction (<30 min) (Table 2). However, these patients did not have more severe reactions during the DBPCFC.
2
Table 1. Demographics of the two groups.
Group 1: time interval ≥30 minutes
n= 37
Group 2: time interval <30 minutes
n= 195
Range Mean Standard deviation
Range Mean Standard deviation
Age (months) 8.0 – 192.0 67.9 48.7 9.0-214.0 85.2 55.2
Specific IgE (kU/L) 0.3-101.0 19,5 28.6 0.3-101.0 27.3 34.7
Frequency Percent Frequency Percent
Sex Male Female 23.0 14.0 62.2% 37.8% 109.0 86.0 55.9% 44.1% Type of food Cashew nut Hazelnut Egg Milk Peanut 4.0 2.0 4.0 16.0 11.0 10.8% 5.4% 10.8% 43.2% 29.7% 36.0 21.0 23.0 47.0 68.0 18.5% 10.8% 11.8% 24.1% 34.9% History of Atopic dermatitis
Positive Negative 34.0 3.0 91.9% 8.1% 170.0 25.0 87.2% 12.8% History of Asthma Positive Negative 19.0 18.0 51.4% 48.6% 107.0 88.0 54.9% 45.1% History of rhinoconjunctivitis Positive Negative 8.0 29.0 21.6% 78.4% 85.0 110.0 43.6% 56.4%
Table 2. Mann Whitney U test analysis of the differences in the dose and severity of reaction for
the two groups.
Group 1: time interval ≥30 minutes
n= 37
Group 2: time interval <30 minutes
n= 195
Median IQR Median IQR P-value
Eliciting dose 1.60 0.27-10.00 0.48 0.05-2.00 0.004 Cumulative dose 2.15 0.37-12.53 0.64 0.07-2.70 0.005 Severity of reaction in DBPCFC 3.00 1.00-5.00 3.00 2.00-6.00 0.214
concluSion
This study has for the first time shown that patients reporting longer time intervals be-tween ingestion and allergic reaction by history (≥30 min) have higher EDs and CDs in DBPCFC compared with those with shorter time intervals (<30 min), which suggests that these patients do indeed accumulate doses in challenge procedures utilizing 30 minute intervals between dose increments. However, this did not result in more severe reactions during the DBPCFC in these patients. These results were not influenced by the possible confounding variables mentioned earlier. Thus, although some patients may accumulate and react to more than one dose of allergenic food, a dosing interval of 30 minutes is long enough to allow this test to be conducted safely in these patients.
2 REfERENCES
1. Sampson HA, Gerth van Wijk R, Bindslev-Jensen C, Sicherer S, Teuber SS, Burks AW et al. Standard-izing double-blind, placebo-controlled oral food challenges: American Academy of Allergy, Asthma & Immunology–European Academy of Allergy and Clinical Immunology PRACTALL consensus report. J Allergy ClinImmunol 2012: 130: 1260–74.
2. Bindslev-Jensen C, Ballmer-Weber BK, Bengtsson U, Blanco C, Ebner C, Hourihane J et al. Standard-ization of food challenges in patients with immediate reactions to foods–position paper from the European Academy of Allergology and Clinical Immunology. Allergy 2004: 59: 690–7.
3. Vlieg-Boerstra BJ, Bijleveld CM, van der Heide S, Beusekamp BJ, Wolt-Plompen SA, Kukler J et al. Development and validation of challenge materials for double-blind, placebo-controlled food chal-lenges in children. J Allergy ClinImmunol 2004: 113: 341–6.
4. Vlieg-Boerstra BJ, van der Heide S, Bijleveld CM, Kukler J, Duiverman EJ, Dubois AE. Placebo reac-tions in double-blind, placebocontrolled food challenges in children. Allergy 2007: 62: 905–12. 5. Taylor SL, Hefle SL, Bindslev-Jensen C, Atkins FM, Andre C, Bruijnzeel-Koomen C et al. A consensus
protocol for the determination of the threshold doses for allergenic foods: how much is too much? Clin Exp Allergy 2004: 34: 689–95.
6. van der Zee T, Dubois A, Kerkhof M, van der Heide S, Vlieg-Boerstra B. The eliciting dose of peanut in double-blind, placebocontrolled food challenges decreases with increasing age and specific IgE level in children and young adults. J Allergy ClinImmunol 2011: 128: 1031–6.
CHAPTER 3
P
REDICTIONOfThEsEvERITyOfALLERGICREACTIONsTOfOODsM. Eleonore Pettersson Gerard H. Koppelman Bertine MJ. Flokstra-de Blok Boudewijn J. Kollen
Anthony EJ. Dubois
ABSTRACT
Background: There is currently considerable uncertainty regarding what the predictors of the severity of diagnostic or accidental food allergic reactions are, and to what extent the severity of such reactions can be predicted.
Objective: To identify predictors for the severity of diagnostic and accidental food allergic reactions and to quantify their impact.
Methods: The study population consisted of children with a double-blind, placebo-con-trolled food challenge (DBPCFC) confirmed food allergy to milk, egg, peanut, cashew nut and/or hazelnut. The data was analyzed using multiple linear regression analysis. Missing values were imputed using multiple imputation techniques. Two scoring systems were used to determine the severity of the reactions.
Results: 734 children were included. Independent predictors for the severity of the DBP-CFC reaction were: age (B=0.04, p=0.001), skin prick test ratio (B=0.30, p<0.001), eliciting dose (B=-0.09, p<0.001), level of specific immunoglobulin E (B=0.15, p<0.001), reaction time during the DBPCFC (B=-0.01, p=0.004), and severity of accidental reaction (B=0.08, p=0.015). The total explained variance of this model was 23.5%, and the eliciting dose only contributed 4.4% to the model. Independent predictors for more severe accidental reac-tions with an explained variance of 7.3% were: age (B=0.03, p=0.014), milk as causative food (B=0.77, p<0.001), cashew as causative food (B=0.54, p<0.001), history of atopic dermatitis (B=-0.47, p=0.006), and severity of DBPCFC reaction (B=0.12, p=0.003). Conclusions: The severity of DBPCFCs and accidental reactions to food remain largely unpredictable. Clinicians should not use the eliciting dose obtained from a graded food challenge for the purposes of making risk-related management decisions.
clinical implications
Clinicians should not assess a patient’s risk of experiencing severe reactions from the eliciting dose obtained from graded food challenges, since eliciting dose only contributes marginally to reaction severity.
3 intRoDuction
Food allergic exposures vary from mild localized reactions to life-threatening anaphylaxis. (1) According to current estimates, approximately 3.1% of all children will experience a severe food allergic reaction.(2) Prediction of the severity of allergic reactions to food is a key issue for medical professionals, patients, policy makers and the food industry to be able to accurately target treatment and improve management and prevention strategies. Thus, efforts have been made to examine possible predictors of severe and/or life-threatening reactions, and recently a review has been published by Turner et al.(3) on this topic. How-ever, the previous studies used for this review have not quantified the contribution of the predictors to reaction severity and have not established them as statistically independent of one another in this regard. In addition, several studies show conflicting results,(4-15) and thus, much uncertainty still remains about the relationship between potential risk factors and the severity of reactions.
Dose has been considered to be an important factor in the development of severe re-actions,(16) although the evidence for this is scant and contradictory. A prior study has suggested that severe reactions during oral food challenges (OFC) tend to occur more frequently with increasing dose levels.(15) Moreover, in a study where the food challenge procedure was allowed to continue after initial mild symptoms, many subjects progressed to anaphylaxis with increasing dose levels.(17) In contrast, Rolinck-Werninghaus et al.(4) concluded that severe reactions may occur at any dose during oral food challenges. Ad-ditionally, patients with prior anaphylaxis to peanut do not seem to have a lower threshold dose than patients with milder reactions.(14,18,19)
It is currently unknown to what extent the severity of food allergic reactions may be predicted by a combined number of readily available clinical factors, such as age, gender, type of allergenic food, level of specific IgE (sIgE), eliciting dose (ED), previous reactions and comorbid atopic disease. Furthermore, it remains uncertain whether more severe reactions tend to occur at higher doses and whether limiting exposure would thus pref-erentially impact severe reactions accordingly. This study aimed at identifying clinically available factors predictive of the severity of reactions in DBPCFCs as well as for the most severe accidental reaction by history. Particular attention was paid to the extent to which the eliciting dose explains the severity of reactions during DBPCFCs.
METhOdS Study population
Data of all positive DBPCFCs in children (2002-2017) was extracted from the Food Chal-lenge Unit Database of our tertiary care pediatric allergy department at Beatrix Children’s Hospital, University Medical Center Groningen (UMCG). The study population consisted of children referred to our center because of suspected food allergy. No children were excluded due to a history of previous anaphylactic reactions. The medical ethics commit-tee of the UMCG deemed that formal medical ethical approval was not required for this study, since all procedures were performed as part of routine clinical care. Extraction of the data on study patients from the food challenge unit database was completed using the following inclusion criterion: a positive DBPCFC on the verum test day according to protocol. (20,21) Additionally, to allow for sufficient power for the food-specific analysis, only challenges conducted with the five most commonly challenged foods were extracted (cow’s milk, hen’s egg, peanut, hazelnut and cashew nut). In children with multiple food challenges, only the first challenge for each food was included.
Double-blind, placebo-controlled oral food challenges
The food challenges were double-blind and placebo-controlled with the suspected food and placebo administered on separate days. The food challenges were conducted accord-ing to previously published methods and protocols. (20-23) In brief, the suspected aller-genic food or placebo was hidden in a food matrix capable of masking sensory detection. (20) The dose of the allergenic food was determined using an incremental scale, specific for the food tested. The doses were given at 30 minute intervals, the dose steps used are displayed in table 1. The food challenge was considered to be positive when objective or repeated or persistent subjective allergic symptoms occurred during the verum test day but not on the placebo day. If symptoms occurring on the verum day were significantly more severe than the symptoms on the placebo day, the food challenge was deemed positive. Unblinding of the test occurred 48 hours after the second food challenge day. Information on the nature and frequency of previous food allergic reactions was obtained in addition to the general atopic history prior to the DBPCFC.
3
Table 1. Dose schemes used during the DBPCFCs.
UMCG (milk, egg), mg protein
UMCG (Peanut, tree nuts), mg protein PRACTALL, mg protein Dose 1 1.75 mg 1.75 mg 1.0 mg Dose 2 3.50 mg 3.50 mg 3.0 mg Dose 3 14 mg 14 mg 10 mg Dose 4 70 mg 70 mg 30 mg Dose 5 350 mg 130 mg 100 mg Dose 6 1750 mg 350 mg 300 mg Dose 7 - - 1000 mg Total 2190 mg 570 mg 1444 mg
Scoring system for the severity of reaction
A scoring system from Astier et al (24) ranging from 0-5, was used for determining the severity of reaction. The symptoms occurring during the verum day of the DBPCFC and of the most severe accidental reaction by history were used to score the severity. Patients were classified according to their most severe symptom and received the correspond-ing grade. Mild symptoms occurrcorrespond-ing at home after leavcorrespond-ing the hospital after 2 hours of symptom-free observation after the DBPCFC on the verum day, were placed in severity grade 0. Children never having consumed the allergic food, and thus never having had an accidental reaction to the food were placed in the severity grade 0 for the accidental reaction. Since there is currently no clear consensus on the use of scoring systems for the severity of allergic reactions, an additional scoring system (25) ranging from 0-12 was used to compare the severity of allergic reactions during the food challenge and the severity of the most severe accidental reaction by history.
Measurement of food-specific igE levels
Serum samples were collected as part of the routine clinical workup for food allergy and were drawn within 6 months of the DBPCFC. The ImmunoCAP system (Thermo Fisher Scientific Inc., Phadia AB, Uppsala, Sweden) was used for determining the level of sIgE. The test was considered positive when a sIgE level of 0.35 kU/L or more was confirmed. Values of >100 kU/L received a designated value of 101 kU/L.
Skin prick tests
Skin prick tests (SPT) were performed with a sterile lancet (ALK-Abelló, Horsholm, Den-mark.) and food allergen extracts (ALK-Abelló, Horsholm, DenDen-mark.) The size of the SPT response was calculated as a mean of the longest diameter and its perpendicular longest diameter measured at 15 minutes. In order to control for possible inter-technician
vari-ability, the ratio of the size of the tested food wheal to the size of the histamine wheal was reported. Any differences in wheal size caused by the device or technician should be similar and thus minimally affect the reported ratio (26).
Statistical analysis
The statistical analysis was performed using the statistics software package IBM SPSS Statistics for Windows, version 23.0. (IBM Corp., Armonk, NY). Multiple linear regression analysis was used to study the relationship between the determinants and the severity of reactions during the DBPCFC as well as those following accidental ingestion. The stepwise backward selection method was used for constructing the prediction model. Alpha was set at 0.05. Only significant factors in the model were considered to be predictors. All assumptions of the tests were met. The determinants were pre-selected for inclusion in the analysis according to previously reported data as well as factors hypothesized to be of influence on the severity of the outcome by the authors. Dummy variables were created for the categorical variable “Type of food” with hazelnut as reference for the regression analysis. Cumulative dose (CD), ED and the level of sIgE were logarithmically transformed before being entered into the analysis in order to comply with the assumptions required for conducting linear regression.
To reduce the probability of bias that might result from excluding missing cases and performing a complete case analysis, missing data was randomly imputed using multiple imputation. A missing value analysis was performed to rule out missing not at random (MNAR) for the included variables. The missing cases for the included variables were in the range of 1-20%. The missing data were replaced using a multiple imputation procedure with a conditional specification, predictive mean matching, 20 iterations and 20 data sets. The use of 20 iterations in the multiple imputation, was based on the variable with the highest number of missing cases. The patient characteristics, severity of reaction and al-lergic features were included as predictors for the multiple imputation.
RESultS
Descriptives of study population
The initial data extraction identified 864 positive DBPCFCs. In children with multiple food challenges to the same food, only the first challenge for each type of food was included (130 cases excluded). Thus a total of 734 children with DBPCFC-confirmed food allergy were included in the final analysis. The median age of the children was 6.2 years, with a range of 0.3 to 18.2 years. The study population consisted largely of boys (59.4%). Of the participating children 87.3% had a doctors diagnosis of atopic dermatitis, 49.7% asthma
3
and 36.6% had previously been diagnosed with allergic rhinoconjunctivitis. The DBPCFCs were performed with peanut (38.7%), cow’s milk (20.4%), cashew nut (17.3%), hen’s egg (12.3%), and hazelnut (11.3%). The level of sIgE ranged from 0.01 to >100.00 kU/L, and was positive in 91.7% of the children. The median reaction time during the DBPCFC was 15.0 minutes, with an IQR of 5.0-50.0.
The interquartile range (IQR) of severity of reaction in the DBPCFC ranged from 1.0-4.0 with a median severity index of 3.0 using the scoring system by Astier et al. Additional demographics categorized according to the severity of the DBPCFC reaction are shown in table 2. The IQR of the severity of the previous accidental reaction by history ranged from 1.0-4.0 and had a median severity index of 3.0. The time interval between accidental ingestion of allergen and allergic reaction by history ranged from 0-2880 minutes in all children, with an IQR of 1.0-15.0 and a median of 5.0 minutes.
Both the CD and the ED were initially included in the analysis. However, these factors showed colinearity during multivariate analysis, thus the CD was excluded from the multi-variate analysis on the basis of the lower explained variance of the model in comparison to the model including the ED (data not shown).
Severity of reaction during DBpcfcs
Using the enter method, a significant model for prediction of the severity of reaction in the DBPCFC emerged (R2 = 0.235, P<0.001). Results from the analyses of the original data and from the pooled data following the multiple imputation procedure can be seen in table 3. After analysis with multiple linear regression, significant independent predictors for the severity of reaction during the DBPCFC were: increasing age (B=0.04, p=0.001), larger SPT ratio (B=0.30, p<0.001), a lower ED (B=-0.09, p<0.001), a higher level of sIgE (B=0.15, p<0.001), a shorter reaction time DBPCFC (B=-0.01, p=0.004), and a more se-vere previous accidental reaction (B=0.08, p=0.015). No significant relationship with the severity of reaction in the DBPCFC was found for gender; type of food; history of atopic dermatitis, asthma or allergic rhinoconjunctivitis; and family history of atopic disease. The total explained variance of this model was 23.5% of the severity of the DBPCFC reaction, and the ED only contributed 4.4% to this explained variance after inclusion in the model (adjusted R2
Table 2. Charact eris tics of the s tudy population ac cording t o the se
verity grade of the DBPCF
C reaction. G rade 0 n=78 G rade1 n=160 G rade 2 n=55 G rade 3 n=171 G rade 4 n=270 A ge ( years ), median (IQR) (5.78) 2.32-11.44 4.76 (2.00-7.63) 6.24 (4.34-9.52) 5.39 (3.16-8.33) 7.99 (5.29-12.12) G ender , n (%) Female 32 (41.0) 69 (43.1) 22 (40.0) 65 (38.0) 110 (40.7) M ale 46 (59.0) 91 (56.9) 33 (60.0) 106 (62.0) 160 (59.3) Food, n (%) C ashew nut 7 (9.0) 19 (11.9) 15 (27.3) 31 (18.1) 55 (20.4) Co w’ s milk 35 (44.9) 45 (28.1) 7 (12.7) 31 (18.1) 32 (11.9) H az elnut 11 (14.1) 17 (10.6) 3 (5.5) 10 (5.8) 42 (15.6) H en ’s egg 3 (3.8) 26 (16.3) 8 (14.5) 36 (21.1) 17 (6.3) Peanut 22 (28.2) 53 (33.1) 22 (40.0) 63 (36.8) 124 (45.9) sI gE (kU/L), median (IQR) 2.71 (0.30-23.20) 2.99 (0.96-14.08) 8.40 (2.11-40.20) 11.75 (2.48-41.80) 12.10 (2.83-51.10) SPT wheal ratio, median (IQR) 1.00 (0.00-1.55) 1.30 (0.90-1.88) 1.30 (0.90-2.00) 1.50 (1.10-2.00) 1.70 (1.30-2.20) ED ( mg pr otein ), median (IQR) 1750.00 (350.00- 1750.00) 98.00 (3.50- 350.00) 139.20 (21.00- 580.00) 70.00 (14.00-350-00) 58.00 (1.75- 307.93) CD ( mg pr otein ), median (IQR) 2189.25 (577.97- 2189.25) 141.12 (5.25-577.97) 226.49 (30.80- 837.52) 89.25 (19.18- 559.58) 83.52 (1.75- 433.68) R
eaction time during the DBPCFC
(minutes ), median (IQR) 55.00 (15.00- 60.00) 25.00 (5.50-60.00) 12.50 (5.00- 32.50) 20.0 (5.00-45.00) 15.0 (5.0-37.0) H istor y of asthma, n (%) Yes 34 (43.6) 70 (43.8) 28 (50.9) 78 (45.6) 155 (57.4) N o 41 (52.6) 89 (55.6) 24 (43.6) 91 (53.2) 110 (40.7)
3 Table 2. Charact eris tics of the s tudy population ac cording t o the se
verity grade of the DBPCF
C reaction. (c on tinued ) G rade 0 n=78 G rade1 n=160 G rade 2 n=55 G rade 3 n=171 G rade 4 n=270 H istor y of atopic der matitis, n (%) Yes 60 (76.9) 150 (93.8) 42 (76.4) 157 (91.8) 232 (85.9) N o 17 (21.8) 9 (5.6) 11 (20.0) 13 (7.6) 36 (13.3) H istor y of rhinoconjunctivitis, n (%) Yes 26 (33.3) 45 (28.1) 14 (25.5) 59 (34.5) 125 (46.3) N o 49 (62.8) 110 (68.8) 38 (69.1) 107 (62.6) 138 (51.1) Sev
erity of most sev
er e accidental reaction, n (%) G rade 0 10 (12.8) 34 (21.3) 11 (20.0) 39 (22.8) 48 (17.8) G rade 1 11 (14.1) 33 (20.6) 6 (10.9) 13 (7.6) 23 (8.50 G rade 2 18 (23.1) 30 (18.8) 10 (18.2) 22 (12.9) 40 (14.8) G rade 3 13 (16.7) 32 (20.0) 12 (21.8) 40 (23.4) 58 (21.5) G rade 4 26 (33.3) 31 (19.4) 16 (29.1) 57 (33.3) 101 (37.4) Ab br eviations: CD , cumulati ve dose; DBPCFC, doub le-b lind place bo contr olled, food challenge; ED , eliciting dose; IQR, interquar tile range; sIgE, specific immuno globulin E; SPT , skin pric k test.
Table 3. Independent predictors for the severity of the DBPCFC reaction (Astier).
Predictor Original data
N=544 R2=0.235
Imputed data – pooled N=734 B 95% CI p-value B 95% CI p-value Age 0.06 0.04 to 0.09 <.001 0.04 0.02 to 0.06 .001 SPT 0.33 0.18 to 0.47 <.001 0.30 0.17 to 0.43 <.001 ED* -0.07 -0.13 to -0.02 .007 -0.09 -0.14 to -0.04 <.001 sIgE* 0.17 0.09 to 0.27 <.001 0.15 0.07 to 0.24 <.001 Reaction time DBPCFC -0.004 -0.01 to
0.00 .037 -0.005 -0.01 to -0.00 .004 Severity of Accidental reaction 0.10 0.03 to 0.17 .005 0.08 0.02 to 0.06 .015
Abbreviations: CI, confidence interval; DBPCFC, double-blind, placebo controlled, food challenge; sIgE, specific im-munoglobulin E; R2, explained variance. *Backtransformed values.
Severity of accidental reactions
A significant model was also found for predicting the severity of reactions following ac-cidental ingestion (R2= 0.073, P<0.001). Results from the analysis of the original data and from the pooled multiple imputation can be seen in table 4. Significant independent pre-dictors for more severe reactions were: increasing age (B=0.03, p=0.014), milk as causative food (B=0.77, p<0.001), cashew as causative food (B=0.54, p<0.001), a negative history of atopic dermatitis (B=-0.47, p=0.006), and a more severe DBPCFC reaction (B=0.12, p=0.003). Thus, children with a history of atopic dermatitis generally had less severe accidental reactions. Having uncontrolled asthma, defined as having daily symptoms; a clinical history of asthma; or allergic rhinoconjunctivitis were not predictive of the severity of the accidental reaction. Moreover, age of onset of food allergy; time interval between ingestion and reaction; and a family history of atopic disease were not predictive of the severity of the accidental reaction (data not shown).
