Agreement Between Oral Glucose Tolerance Test and HbA1c in Diagnosing Prediabetes among Asian Indians

Abstract Context: Little is known about the agreement between the oral glucose tolerance test (OGTT) and HbA1c in diagnosing prediabetes among Asian Indians. Aims: To evaluate the agreement between OGTT- and HbA1c-based prediabetes phenotypes in an Indian population. Settings and Design: A cross-sectional analysis was conducted using data from 1120 individuals with prediabetes who participated in the baseline survey of the Kerala Diabetes Prevention Program in India. Materials and Methods: OGTT-based prediabetes phenotypes included impaired fasting glucose (IFG: fasting plasma glucose 100–125 mg/dL) and impaired glucose tolerance (IGT: 2 h plasma glucose 140–199 mg/dL). The HbA1c-defined phenotype was characterized by an HbA1c level of 5.7–6.4% (“elevated HbA1c”). Agreement between OGTT and HbA1c for diagnosing prediabetes was assessed using Cohen’s kappa statistic, and the overlap between prediabetes phenotypes was visualized with Venn diagrams. Results: The mean age of participants was 46.1 years (SD: 7.7), and 62.6% were male. The majority (87.8%) were classified as having OGTT-based prediabetes, whereas less than half (45.4%) were identified with HbA1c-based prediabetes. Only 65 individuals (5.8%) fulfilled all three criteria (IFG, IGT, and elevated HbA1c), and Cohen’s kappa was 0.09. Conclusion: The agreement between OGTT and HbA1c in diagnosing prediabetes was minimal in this Indian population.