Utility of glycated hemoglobin in diagnosing type 2 diabetes mellitus: a community-based study.

Abstract

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. 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. Community based randomized cross sectional study in urban Chandigarh, a city in north India, from April 2008 to August 2009. Subjects included 1972 subjects aged 20 yr or older. Intervention included an oral glucose tolerance test and glycated hemoglobin in all the subjects. Utility of HbA1c as a diagnostic method in newly detected diabetes mellitus subjects was evaluated. 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 90.4 and 94.4%, respectively, for diagnosis of newly detected diabetes mellitus. 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.