Combining HbA(1c) and glycated albumin improves detection of dysglycaemia in mixed-ancestry South Africans

BACKGROUND: Combining HbA(1c) with glycated albumin (GA) may improve detection of dysglycaemia. As BMI correlates positively with HbA(1c) and negatively with GA, HbA(1c) 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/m(2) (range 15.6–73.8); obesity 39.9% and no prior diabetes history) the: (1) correlation of BMI with HbA(1c) and GA, (2) ability of HbA(1c) 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 HbA(1c) and GA. FINDINGS: Normal glucose tolerance, prediabetes and diabetes occurred in 76%, 17% and 7%, respectively. BMI positively correlated with HbA(1c) [r = 0·34 [95%CI: 0·29,0·39)] and negatively with GA [-0·08 (0·13,0·03)]. For HbA(1c) 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, HbA(1c)-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: HbA(1c)+GA detected: 69% (60,76), 82% (75,87) and 76% (71, 81). Therefore, for the total cohort detection of dysglycaemia HbA(1c)-alone vs HbA(1c)+GA detected 63% (57,68) vs 76% (71,81). INTERPRETATION: The opposite correlations of HbA(1c) and GA with BMI have now been demonstrated in an African-based population. Improving detection of dysglycaemia by combining HbA(1c) and GA has important implications for diabetes risk screening. FUNDING: AES is supported by the intramural programs of the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Minority Health and Health Disparities of the National Institutes of Health (NIH, Bethesda, Maryland, USA). DBS is supported by the intramural program of the Clinical Center of NIH. The South African Medical Research Council (SAMRC) funded the VMH study with funds from the National Treasury under its Economic Competitiveness and Support Package (MRC-RFA-UFSP-01–2013/VMH Study).