IFCC-HbA1c May Be More Useful than NGSP-HbA1c in the Comparison between HbA1c Values in Variant Hemoglobin with a Mutation on α Chain and β Chain.

HbA1c values in variant hemoglobin with a mutation on alpha chain and beta chain are assumed to be different because the alpha chain and beta chain of the globin gene have two and one gene(s), respectively. We examined whether the differentiation between HbA1c values in variant hemoglobin with a mutation on a chain (C1 alpha) and beta chain (C1 beta) is possible. Three patients with C1 alpha and 9 patients with C1 beta were included. HbA1c was measured by standard mode high-performance liquid chromatography (HPLC) (HPLC-HbA1c) and immunoassay (IA: IA-HbA1c). Glycated albumin (GA) was determined, and each ratio was compared. HbA1c is expressed in National Glycohemoglobin Standardization Program (NGSP) units (A1C) and International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (iA1c). Both the HPLC-A1C/IA-A1C ratio and the HPLC-iA1c/IA-iA1c ratio in C1 alpha were significantly lower than those in C1 beta. Although there were no significant differences between the GA/HPLC-A1C ratios in both groups, the GA/HPLC-iA1c ratio in C1 alpha was significantly higher than those in C1 beta. If the cutoff values for the HPLC/IA-iA1c ratio and GA/HPLC-iA1c ratio were set at 65% and 5.3, respectively, both sensitivity and specificity were 100%. Differentiation between C1 alpha and C1 beta might be possible by using the HPLC-iA1c/IA-iA1c ratio or GA/HPLC-iA1c ratio.