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HbA1c, diabetic retinopathy relationship supports cut-point diagnosis in Asians
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The use of HbA1c levels to diagnose diabetes is appropriate among Asian populations, according to research published in The Journal of Clinical Endocrinology & Metabolism.
A 6.5% cut point performed reasonably well in analyses of major Asian ethnic groups, despite variation in the relationship between HbA1c and diabetic retinopathy, according to researchers.
“In this large study of more than 13,000 Chinese, Malays and Indian adults, HbA1c provides good discrimination between individuals with and without moderate retinopathy,” the researchers wrote.
Charumathi Sabanayagam, MD, MPH, PhD, of the Singapore Eye Research Institute, and colleagues looked at four population-based, cross-sectional studies involving 5,834 Chinese, 3,596 Malaysian and 3,740 Indian adults aged at least 25 years. The studies, conducted from 2004 to 2011, included the Singapore Malay Eye Study, Singapore Indian Eye Study, Singapore Chinese Eye Study and Singapore Prospective Study Program.
The investigators assessed diabetes-specific moderate retinopathy through digital retinal photographs and defined the condition as level >43 on the Early Treatment Diabetic Retinopathy Study scale. Sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) were compared across ethnic groups at various HbA1c cut points, along with the area under the receiver operating characteristic curve (AUC) for detecting moderate retinopathy.
Indians and Malays had higher HbA1c levels compared with Chinese (P<.001). With HbA1c levels <6.5%, the prevalence of moderate retinopathy was <1% in all ethnic groups.
With HbA1c levels ≥6.5%, the sensitivity for detecting moderate retinopathy was lower in Chinese (75.8) vs. Indians (86%) and Malays (85.3%) but specificity was higher (89.7% for Chinese vs. 71.9% for Indians and 76.3% for Malays). However, the groups demonstrated similar PPV (10.5% for Chinese, 12.3% for Indians and 12.4% for Malays) and NPV (99.6% for Chinese, 99.1% for Indians and 99.2% for Malays).
The AUCs were similar across the groups (0.861 for Chinese, 0.851 for Indians and 0.853 for Malays).
“In Malays and Indians, a small increase in the threshold may give greater PPV with only a small impact on the NPV,” the researchers wrote. “However, the benefits of this, given the added complexity that it introduces, is not clear and should be considered in the light of cost-effectiveness of earlier diagnosis and treatment, and resource constraints of the health care systems in Asia.”
Disclosure: The researchers report no relevant financial disclosures.
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