S-Alc
0 3 0 6 0 0 3 0 6 0 0 3 0 6 0
HbAD High HbF
HbAAS-Rlc
0 s o 6 0 0 :- HJ 6 0
Figure 1.
HA-81 BOV chromatograms of hemoglobin types S, C, E, D, and F in comparison to hemoglobin A.
Reproducibility and trueness in a regular EQA programme
The samples of the 2009 federate programme (national EQA organisers share samples and software but keep their own identity) of the Netherlands (SKML), Belgium (WIV), Greece (ESEAP), and Finland (Lab quality) were analysed with the HA-81 80V. The EQA programme consists of 24 specimens (1 2 blinded duplicates).
IFCC targets and derived NGSP targets for the programme are set using the IFCC Reference Measurement Procedure. The precision of labs is calculated from the 1 2 blind duplicates and expressed as CV. Trueness is defined as the difference between measured HbA1c and the target. Table 6 shows the CV and the bias from the target (at an HbA1c concentration of 54 mmol/mol/ 7.0%) for the HA-81 80V in comparison to the mean CVs as determined for the major methods in the EQA programme.
94
Table 6: ARKRA Y HA-81 BOV: Reproducibility and Trueness compared with other methods*
Deviation Target
Method n CV I FCC NGSP
mmol/mol %
Major Methods 2009
ARKRA Y HA-81 80 0.8% 0 0.0
ARKRAY HA 8160 1 57 1 .3% +1 +0.1
ARKRAY HA 8140 33 2.1 % +2 +0.2
TOSOH GB 35 0.9% +1 +0. 1
TOSOH G7 48 1 .3% +1 +0.1
TOSOH GS 8 2.0% +1 +0. 1
Bio-Rad D10 17 2.4% +1 +0.1
Bio-Rad Variant 41 1 .8% +1 +0.1
Roche Tina Quant 73 2.8% +1 +0. 1
Historical Performance
All methods 1 993 1 22 5.2%
All methods 1 999 143 4.9% +3 +0.3
All methods 2005 376 2.9% -2 -0.2
All methods 2009 438 1 .8% +1 +0.1
* o n basis of the 2009 EQA programme of ERL (European Reference Laboratory)
Discussion
Therapeutic strategies rely more than ever on reproducible and unbiased measurement of HbA1c- Not only for control and follow-up of diabetic patients, but recently also for diagnosis and screening(5)_ The efforts of the IFCC working group(11>
on standardisation of HbA1c have contributed much to global standardisation.
The efforts of manufacturers contributed to improvements of analytical systems and are in fact ongoing to create the fastest, most convenient and most reliable test. In this study, we evaluated the HA-8180V, the new, fifth generation analyser from ARKRAY/Menarini. With between-run CVs of 0.2% - 0.4%, within-run CVs of 0.2%, and total CVs of 0.4% - 0.7% the evaluation revealed excellent reproducibility, far below the most stringent requirements of 2%(12). Trueness verification of the manufacturer-calibrated instrument demonstrated traceability to the IFCC and NGSP reference measurement procedures. Evaluation of linearity, carry-over and linearity showed good results. There was no trace of interference by the common interferences (labile- HbA1c, carbamylated hemoglobin, icteric samples, hematocrit).
However, some statistical tests showed significant differences. It seems a paradox, but these are derived from the excellent reproducibility of the instrument:
HbA1c results are reported with no decimals (IFCC units) and to one decimal (NGSP units). From a statistical point of view, one additional decimal is required, but this is clinically irrelevant.
Hemoglobin variants are an important issue. They can interfere with HbA1c measurements, but when detected, provide essential information on the presence of a variant: important for the interpretation of the HbA1c result and for genetic counselling. We evaluated the HA-8180V for both applications. Hemoglobin variants AS, AC and F did not affect the correct measurement of HbA1c- However, in patients with AE and AD, HbA1c cannot be measured. All five variants are easily recognised in the chromatogram, and correctly interpreted by the instrument (the correct name of the variant is reported).
The evolution of the quality of methods is illustrated by the performance of the various instruments in the federative EQA programme of The Netherlands, Belgium, Greece and Finland: the third generation instrument of ARKRAY (HA-81 40) has a mean intra-lab CV of 2. 1 %. The fourth generation (HA-8160) has a CV of 1 .3% and the fifth generation (HA-8180 evaluated in this study) has a CV as low as 0.8%. The continuous improvement in quality is also demonstrated by the overall interlab CV over the past 15 years: from 5.2% in 1993 to 1 .8% in 2009.
Excellent reproducibility is a prerequisite for the application of HbA1c in diagnosis and screening of diabetes. The final conclusion from this evaluation is that the new ARKRAY/Menarini instrument performs at a high level, and is fit for any clinical application of
HbA1c-96
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