STANDARDIZATION OF GLYCATED HEMOGLOBIN ASSAYS THROUGHOUT THE NORTHERNREGION OF ENGLAND - A PILOT-STUDY

We describe a pilot study designed to assess the comparability of meas urements of glycated haemoglobin among 15 laboratories in the North of England. We also evaluated a means of improving agreement and alignin g results by referencing locally measured values to those obtained by the central biochemistry laboratory of the Diabetes Control and Compli cations Trial research group. Blood samples from 50 diabetic and non-d iabetic subjects were analysed for glycated haemoglobin content in the participating and reference laboratories using a variety oi: routinel y available methods, The mean CV for these results was 15.3 % (95 % co nfidence interval 14.0 % to 16.5 %). Using a regression equation relat ing a subset of seven (pi these results to their assigned reference va lues, a glycated haemoglobin index was calculated for all the other sa mples distributed. The mean interlaboratory CV improved to 4.6 % (95 % confidence interval 4.0 % to 5.1 %), p<0.0001. The percentage bias of results from the reference method also improved from 15.1 % (95 % con fidence interval 9.4 to 20.1) to 4.67 % (95 % confidence interval 4.05 to 5.25) after alignment, p<0.001. This study demonstrated that subst antial method related differences between reported glycated haemoglobi n results exist. These carr be reduced using a simple calibration stra tegy in which data are correlated to an established method with associ ated extensive clinical interpretive value as established by the DCCT. (C) 1997 by John Wiley & Sons, Ltd.