Utility of Glycated Hemoglobin in Diagnosing Type 2 Diabetes Mellitus: A Community-Based Study

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Abstract
Context: Although glycated hemoglobin (HbA1c) has recently been incorporated as a diagnostic test by the American Diabetes Association, its validity needs to be established in Asian Indians in a community setting. Objective: The objective of the study was to assess the validity of HbA1c as a screening and diagnostic test in individuals with newly detected diabetes mellitus. Design and Setting: Community based randomized cross sectional study in urban Chandigarh, a city in north India, from April 2008 to August 2009. Subjects: Subjects included 1972 subjects aged 20 yr or older. Intervention: Intervention included an oral glucose tolerance test and glycated hemoglobin in all the subjects. Main Outcome Measures: Utility of HbA1c as a diagnostic method in newly detected diabetes mellitus subjects was evaluated. Results: Using World Health Organization criteria for diagnosis of diabetes mellitus, 134 (6.7%) had newly detected diabetes mellitus, 192 (9.7%) known diabetes mellitus, 329 (16.6%) prediabetes, and 1317 (69.4%) were normal of 1972 people screened. Using only the ADA criteria, 38% people were underdiagnosed. An HbA1c level of 6.1% had an optimal sensitivity and specificity of 81% for diagnosing diabetes. A HbA1c level of 6.5% (±2 sd) and 7% (±2.7 sd) had sensitivity and specificity of 65 and 88% and 42 and 92%, respectively, with corresponding positive predictive value and negative predictive value of 75.2 and 96.5% and 90.4and 94.4%, respectively, for diagnosis of newly detected diabetes mellitus. Conclusion: A HbA1c cut point of 6.1% has an optimal sensitivity and specificity of 81% and can be used as a screening test, and a cut point of 6.5% has optimal specificity of 88% for diagnosis of diabetes.