Combining HbA1c and glycated albumin improves detection of dysglycaemia in mixed-ancestry South Africans

Abstract

Background Combining HbA1c with glycated albumin (GA) may improve detection of dysglycaemia. As BMI correlates positively with HbA1c and negatively with GA, HbA1c may be more effective in obese and GA in nonobese individuals. Methods To relate these findings to Africans, we assessed in 1274 South Africans living in CapeTown (male 26%; age 48§16y; BMI 28.7 kg/m2 (range 15.6−73.8); obesity 39.9% and no prior diabetes history) the: (1) correlation of BMI with HbA1c and GA, (2) ability of HbA1c and GA separately and jointly, to detect OGTT-diagnosed dysglycaemia (diabetes plus prediabetes). Data collection took place between 2014 and 2016 in the City of Cape Town. Dysglycaemia was diagnosed by glucose criteria for the OGTT. Youden index was used to optimize diagnostic thresholds for HbA1c and GA. Findings Normal glucose tolerance, prediabetes and diabetes occurred in 76%, 17% and 7%, respectively. BMI positively correlated with HbA1c [r = 0¢34 [95%CI: 0¢29,0¢39)] and negatively with GA [-0¢08 (0¢13,0¢03)]. For HbA1c the optimal threshold by Youden-index for dysglycaemia diagnosis was: 6¢0% (95%CI: 5¢8,6¢2) and for GA: 13¢44% (12¢72,14¢71). In the nonobese, obese and total cohort, HbA1c-alone detected: 51% (42−60), 72% (65,78), 63% (57,68), respectively; GA-alone detected 55% (52% (46,63), 52% (44, 59) and 53% (47,53), respectively; whereas: HbA1c+GA detected: 69% (60,76), 82% (75,87) and 76% (71, 81). Therefore, for the total cohort detection of dysglycaemia HbA1c-alone vs HbA1c+GA detected 63% (57,68) vs 76% (71,81). Interpretation The opposite correlations of HbA1c and GA with BMI have now been demonstrated in an Africanbased population. Improving detection of dysglycaemia by combining HbA1c and GA has important implications for diabetes risk screening.