Improved detection of abnormal glucose tolerance in africans: The value of combining hemoglobin a1c with glycated albumin

Abstract

OBJECTIVE In African-born Blacks living in America, we determined by BMI category 1) prevalence of abnormal glucose tolerance (Abnl-GT) and 2) diagnostic value and reproducibility of hemoglobin A1c (HbA1c), fructosamine, and glycated albumin (GA). RESEARCH DESIGN AND METHODS Participants (n 5 416; male, 66%; BMI 27.7 6 4.5 kg/m2 [mean 6 SD]) had an oral glucose tolerance test with HbA1c, GA, and fructosamine assayed. These glycemic markers were repeated 11 6 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 HbA1c, GA, and fructosamine were the values at the 75th percentile for the population (39 mmol/ mol [5.7%], 14.2%, and 234 mmol/L, respectively). RESULTS Abnl-GT prevalence in the nonobese was 34% versus 42% in the obese (P 5 0.124). Reproducibility was excellent for HbA1c and GA (both k ‡ 0.8), but moderate for fructosamine (k 50.6). Focusing on HbA1c and GA in the nonobese, we found as single tests the sensitivities of HbA1c and GA were 36% versus 37% (P 5 0.529). Combining HbA1c and GA, sensitivity increased to 58% because GA identified 37% of Africans with Abnl-GT not detected by HbA1c (P value for both tests vs. HbA1c alone was <0.001). For the obese, sensitivities for HbA1c, GA, and the combined tests were 60%, 27%, and 67%, respectively. Combined test sensitivity did not differ from HbA1c alone (P 5 0.25) because GA detected only 10% of obese Africans with Abnl-GT not detected by HbA1c. CONCLUSIONS Adding GA to HbA1c improves detection of Abnl-GT in nonobese Africans.