Key result
IFCC HbA1c values correlate strongly with DCCT values despite yielding significantly lower reference ranges.
Observational
Effect estimate: r = 0.999
The IFCC reference materials and method show excellent correlation with existing methods but yield lower absolute values, suggesting they should be used to calibrate present methods to established DCCT levels.
Clinicians should retain DCCT-aligned HbA1c reporting; leaves open effects of IFCC calibration on targets and outcomes.
The results of Finnish HbA(1C) surveys (Labquality Ltd.) during the past 10 years have undergone continuous improvement with smaller overall coefficients of variation for the HbA(1C) mean values of all methods (from 7.5 to 5.4% for normal and from 8.9 to 4.7% for diabetic samples). Most of the HbA(1C) methods are certified for traceability to the Diabetes Control and Complication Trial (DCCT) designated comparison method, which originally was a high-performance liquid chromatography (HPLC) method (Bio-Rex 70, Bio-Rad) but is no longer in routine use. It was therefore important that the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) had prepared both reference preparations and method for the determination of HbA(1C). However, the very demanding reference method is not realistic for use in clinical laboratories. According to the present study, the mean HbA(1C) values of the Labquality Ltd. showed significant correlations to the HbA(1C) values of The European Reference Laboratory for Glycohemoglobin (r = 0.999) and to the values using the IFCC method (r = 0.999). The reference values of the IFCC method (mainly those of the manufacturer) range from 2.85 to 3.81%, being significantly lower than the present DCCT values (4.0-6.1%). Since it may take some time before consumers are ready to accept the new IFCC reference values for general use, we propose that the IFCC reference materials and method should be used for calibration of the present methods to the well-known DCCT levels.
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Penttilä et al. (2005) conducted an observational in HbA1c analysis. IFCC reference method vs. DCCT method was evaluated on Correlation of mean HbA1c values (r = 0.999). Mean HbA1c values from Finnish surveys showed significant correlations to the IFCC method (r = 0.999), although IFCC reference values are significantly lower than DCCT values.
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