Three assays for glycohemoglobin compared.
Using 123 specimens, we compared the concordance of three different methods for determining glycohemoglobin (GHb): the Diamat (Bio-Rad Laboratories), an automated analyzer measuring HbA1c by cation-exchange chromatography; an assay with the IMx analyzer (Abbott Laboratories), based on boronate affinity binding; and an HPLC method measuring HbA1c by cation-exchange chromatography on a PolyCAT A column (PolyLC Inc.). The Pearson's correlation coefficient between PolyCAT A and Diamat was 0.900 +/- 0.038 (mean +/- 2 SD) and between PolyCAT A and IMx, 0.857 +/- 0.042. However, up to twofold differences were seen in some samples. The proportion of GHb was consistently lower with the PolyCAT A method than with the other two assays, apparently because of better separation of HbA1c from nonglycated coeluting forms of Hb. The difference in glycation percentage between the PolyCAT A and Diamat methods is 2-3% over the whole concentration range. These results point to the limitations of Diamat as a reference method to be used to calibrate other methods for determining HbA1c. Further, a switch from one method to another is likely to cause considerable problems in the clinical follow-up of certain patients.
Turpeinen
U
U
Helsinki University Central Hospital, Laboratory, Finland.
Karjalainen
U
U
Stenman
U H
UH
D001322:Autoanalysis / Q000379:methods / Q000706:statistics & numerical data; D001897:Boronic Acids; D002412:Cations; D002846:Chromatography, Affinity / Q000706:statistics & numerical data; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000706:statistics & numerical data; D002852:Chromatography, Ion Exchange / Q000706:statistics & numerical data; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D012016:Reference Values; D012680:Sensitivity and Specificity
D001897:Boronic Acids; D002412:Cations; D006442:Glycated Hemoglobin