Effects of Hemoglobin C and S Traits on Seven Glycohemoglobin Methods

Abstract
Glycohemoglobin (gHb) is a marker of long-term glycemic control that has been shown to correlate with complications of diabetes mellitus (1). The National Glycohemoglobin Standardization Program (NGSP) was established to standardize gHb results so that clinical laboratory results are comparable to those reported by the Diabetes Control and Complications Trial (2)(3). Previous studies have shown that some gHb methods yield inaccurate results with samples heterozygous for hemoglobin (Hb) C or Hb S (4)(5)(6). At least 10% of black Americans have either Hb C or S trait, and there were 19 million black Americans over age 19 in 1990 (7)(8)(9)(10). The prevalence of diabetes is estimated to be 5.1% of the adult population, with the rate for non-Hispanic blacks being 1.6-fold higher than that of non-Hispanic whites (11). It is therefore probable that at least 150 000 Americans with diabetes have Hb C or S trait. Here, we investigate the measurement of gHb in specimens containing Hb C or S trait using eight gHb methods currently in clinical use.