Annalise E Zemlin1, Marizna Barkhuizen2, Andre P Kengne3, Rajiv T Erasmus2, Tandi E Matsha4. 1. Department of Pathology, Chemical Pathology Division, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa. Electronic address: azemlin@sun.ac.za. 2. Department of Pathology, Chemical Pathology Division, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa. 3. Department of Medicine, Faculty of Health Science, University of Cape Town, Observatory, South Africa; Non-Communicable Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa. 4. Department of Biomedical Sciences, Cape Peninsula University of Technology, South Africa. Electronic address: matshat@cput.ac.za.
Abstract
OBJECTIVE: To assess the utility of glycated albumin (GA%) as a diagnostic marker of type 2 diabetes and prediabetes in an African population. METHODS: GA% levels were determined in a sample of 1294 mixed ancestry adults (74.2% women) residing in Cape Town using an enzymatic method. The participants' glycemic status was based on oral glucose tolerance test (OGTT). RESULTS: The mean age was 47.8 years with a mean body mass index (BMI) of 28.7 kg/m2. Obesity was more pronounced in the screen-detected diabetes and prediabetes groups with mean BMI's of 32.5 kg/m2 and 31.5 kg/m2 respectively. The optimal thresholds of GA% to diagnose screen-detected diabetes and prediabetes, were 14.90% and 12.75% respectively. For screen-detected diabetes, the C-statistic was higher for HbA1c than GA% (p = .034) with values of 0.899 (95% CI 0.855-0.943) and 0.873 (0.782-0.892) respectively. The agreement between GA% and HbA1c at their optimal thresholds for diagnosing screen-detected diabetes, was kappa = 0.33 (95% CI 0.26-0.40) and was higher than the agreement for prediabetes, kappa = 0.16 (0.11-0.21). The performance of GA% to identify screen-detected diabetes at the optimal threshold of 14.90%, was 64.8% (95% CI 54.1%-74.6%) for sensitivity and 93.5% (92.0%-94.9%) for specificity. GA% was significantly less sensitive, but more specific than HbA1c (at the optimal threshold of 6.15%) for screen-detected diabetes diagnosis (both p ≤ .002 from McNemar tests for sensitivity and specificity comparisons). CONCLUSIONS: GA% performed less well than HbA1c to identify participants with OGTT-diagnosed type 2 diabetes or prediabetes (HbA1c cut-off of 6.15% and 5.95% respectively) in this population.
OBJECTIVE: To assess the utility of glycated albumin (GA%) as a diagnostic marker of type 2 diabetes and prediabetes in an African population. METHODS:GA% levels were determined in a sample of 1294 mixed ancestry adults (74.2% women) residing in Cape Town using an enzymatic method. The participants' glycemic status was based on oral glucose tolerance test (OGTT). RESULTS: The mean age was 47.8 years with a mean body mass index (BMI) of 28.7 kg/m2. Obesity was more pronounced in the screen-detected diabetes and prediabetes groups with mean BMI's of 32.5 kg/m2 and 31.5 kg/m2 respectively. The optimal thresholds of GA% to diagnose screen-detected diabetes and prediabetes, were 14.90% and 12.75% respectively. For screen-detected diabetes, the C-statistic was higher for HbA1c than GA% (p = .034) with values of 0.899 (95% CI 0.855-0.943) and 0.873 (0.782-0.892) respectively. The agreement between GA% and HbA1c at their optimal thresholds for diagnosing screen-detected diabetes, was kappa = 0.33 (95% CI 0.26-0.40) and was higher than the agreement for prediabetes, kappa = 0.16 (0.11-0.21). The performance of GA% to identify screen-detected diabetes at the optimal threshold of 14.90%, was 64.8% (95% CI 54.1%-74.6%) for sensitivity and 93.5% (92.0%-94.9%) for specificity. GA% was significantly less sensitive, but more specific than HbA1c (at the optimal threshold of 6.15%) for screen-detected diabetes diagnosis (both p ≤ .002 from McNemar tests for sensitivity and specificity comparisons). CONCLUSIONS:GA% performed less well than HbA1c to identify participants with OGTT-diagnosed type 2 diabetes or prediabetes (HbA1c cut-off of 6.15% and 5.95% respectively) in this population.
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