Improved Detection Of Abnormal Glucose Tolerance In Africans: The Value Of Combining Hemoglobin A(1c) With Glycated Albumin

OBJECTIVE In African-born Blacks living in America, we determined by BMI category1) prevalence of abnormal glucose tolerance (Abnl-GT) and2) diagnostic value and reproducibility of hemoglobin A(1c)(HbA(1c)), fructosamine, and glycated albumin (GA). RESEARCH DESIGN AND METHODS Participants (n= 416; male, 66%; BMI 27.7 +/- 4.5 kg/m(2)[mean +/- SD]) had an oral glucose tolerance test with HbA(1c), GA, and fructosamine assayed. These glycemic markers were repeated 11 +/- 7 days later. Abnl-GT diagnosis required 0 h >= 5.6 mmol/L (>= 100 mg/dL) and/or 2 h >= 7.8 mmol/L (>= 140 mg/dL). Thresholds for HbA(1c), GA, and fructosamine were the values at the 75th percentile for the population (39 mmol/mol [5.7%], 14.2%, and 234 mu mol/L, respectively). RESULTS Abnl-GT prevalence in the nonobese was 34% versus 42% in the obese (P= 0.124). Reproducibility was excellent for HbA(1c)and GA (both kappa >= 0.8), but moderate for fructosamine (kappa = 0.6). Focusing on HbA(1c)and GA in the nonobese, we found as single tests the sensitivities of HbA(1c)and GA were 36% versus 37% (P= 0.529). Combining HbA(1c)and GA, sensitivity increased to 58% because GA identified 37% of Africans with Abnl-GT not detected by HbA(1c)(Pvalue for both tests vs. HbA(1c)alone was <0.001). For the obese, sensitivities for HbA(1c), GA, and the combined tests were 60%, 27%, and 67%, respectively. Combined test sensitivity did not differ from HbA(1c)alone (P= 0.25) because GA detected only 10% of obese Africans with Abnl-GT not detected by HbA(1c). CONCLUSIONS Adding GA to HbA(1c)improves detection of Abnl-GT in nonobese Africans.