CALIBRATION OF ION-EXCHANGE HPLC MEASUREMENTS OF GLYCOHEMOGLOBIN - EFFECT ON INTERASSAY PRECISION

To investigate the effect of calibration with lyophilized calibrators on the interassay precision of glycohemoglobin (glyHb) measurements, w e used an ion-exchange HPLC system equipped with a Pharmacia Mono S(R) HR 5/5 column. Calibration of analytical runs substantially increased interassay variation (CV), from 1.7% to 4.4% and from 0.9% to 3.2% fo r control samples with low (6.5%) and high (14%) glyHb percentages, re spectively. Standardization of glyHb results, though essential for int erlaboratory comparisons, should not be done at the expense of assay p recision, as may occur with thoughtless use of lyophilized calibrators . We therefore recommend the use of carefully determined conversion fa ctors for standardization of glyHb results obtained with ion-exchange HPLC systems that are capable of excellent long-term interassay precis ion.