Effects of 7 hemoglobin variants on the measurement of glycohemoglobin by 14 analytical methods.

BACKGROUND Hemoglobin variants (Hb(VAR)) are not uncommon in the Korean population, with Hb G-Coushatta and Hb Queens being the 2 most common Hb(VAR). Hb G-Coushatta is also the most common Hb(VAR) in Chinese people from the Silk Road region, as well as in some North American Indian tribes. However, data are scarce on the effect of these Hb(VAR) on the different methods used for analyzing HbA(1c). METHODS Specimens from 24 individuals with 7 Hb(VAR) (Hb G-Coushatta, Hb Queens, Hb G-Hsi-Tsou, Hb Ube-4, Hb G-Waimanalo, Hb Inglewood, and Hb Bologna-St.Orsola) were collected and tested using the International Federation of Clinical Chemistry primary reference method as well as 14 routine HbA(1c) assay methods. RESULTS Hb G-Coushatta showed a clinically significant effect on the measured HbA(1c), particularly when analysis was performed with ion-exchange HPLC methods with short elution times. This interference could be resolved by measuring the HbA(1c) using other methods such as HPLC with a long elution time, immunoassay, boronate affinity chromatography, and enzymatic assay. Hb Queens showed a clinically significant difference, defined as a >10% deviation from regression lines, in results from the 2 HPLC methods but not in the other methods. The remaining 5 rare Hb(VAR) showed different HbA(1c) results in the different assays. CONCLUSION Hb G-Coushatta, Hb Queens, and other rare Hb(VAR) can interfere with glycohemoglobin assays, including ion-exchange HPLC methods with short elution times, but the interference can be resolved using other unaffected methods. It is important to identify these Hb(VAR) through a careful inspection of the chromatograms and apply other noninterfering methods for accurate measurements of the HbA(1c).