Improved Detection of Abnormal Glucose Tolerance in Africans: The Value of Combining Hemoglobin A1c with Glycated Albumin

Objectives: In African-born blacks living in America, we determined by BMI category: (a) prevalence of Abnl-GT; (b) diagnostic value and reproducibility of HbA_1c, fructosamine and GA.

Methods: Participants (n=416, male: 66%; BMI: 27.7±4.5kg/m² (mean±SD)) had OGTT with HbA_1c, GA, and fructosamine assayed. These glycemic markers were repeated 11±7d later. Abnl-GT diagnosis required: 0h≥5.6mmol/L (≥100 mg/dL) and/or 2h≥7.8mmol/L (≥140 mg/dL). Thresholds for HbA_1c, GA and fructosamine were the values at the 75^th percentile for the population (39 mmol/mol (5.7%), 14.2%, 234µmol/L, respectively).

Results: Abnl-GT prevalence in the nonobese and obese were: 34% vs. 42%, (P=0.124). Reproducibility was excellent for HbA_1c and GA (both κ≥0.8), but moderate for fructosamine (κ=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% vs. 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 (P-value: both tests vs. HbA_1c alone <0.001). For the obese, sensitivities for HbA_1c, GA and the combined tests were: 60%, 27%, 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.

Conclusion: Adding GA to HbA_1c improves detection of Abnl-GT in nonobese Africans.