Discordance between HbA 1C and Glucose Tests for the Diagnosis of Prediabetes in a Filipino-American Cohort

Abstract Introduction The diagnostic utility of HbA1c for identifying prediabetes remains uncertain, particularly across diverse racial and ethnic populations. We evaluated concordance between HbA1c, fasting plasma glucose (FPG), and oral glucose tolerance testing (OGTT) in a Filipino-American cohort. Research Design and Methods We analyzed cross-sectional data from 149 Filipino-American adults without known diabetes in the San Francisco Bay Area. Prediabetes prevalence was assessed using American Diabetes Association criteria for HbA1c, FPG, and OGTT. Agreement between diagnostic methods was evaluated, and metabolic characteristics were compared across glycemic categories. Results Prediabetes prevalence differed substantially by diagnostic method: 35% by HbA1c, 8.1% by FPG, and 8.7% by OGTT. Overall agreement between tests was low. Among individuals classified as prediabetic by HbA1c, the majority did not meet criteria by FPG or OGTT. However, higher HbA1c levels were associated with increased body mass index, waist-hip ratio, blood pressure, triglycerides, fasting insulin, and HOMA-IR. Conclusions In this Filipino-American cohort, HbA1c identifies a substantially larger group of individuals with prediabetes compared to glucose-based tests, with limited concordance between methods. Individuals classified as prediabetic by HbA1c exhibit features consistent with insulin resistance. These findings highlight potential differences in metabolic phenotypes captured by alternative diagnostic criteria and underscore the need for longitudinal studies to determine their relative prognostic value. 1) What is already known on this topic HbA1c, FPG, and OGTT are all used to diagnose prediabetes, but prior studies show poor agreement between these tests and substantial variation in prevalence estimates across populations. Evidence suggests these differences may be influenced by underlying physiology and race/ethnicity, yet data in Filipino-Americans—especially for prediabetes—have been limited. 2) What this study adds In Filipino-Americans, HbA1c identifies a much higher prevalence of prediabetes than FPG or OGTT, with low concordance between methods. Individuals classified as prediabetic by HbA1c alone show metabolic features consistent with insulin resistance, suggesting this group represents a meaningful at-risk phenotype. 3) How this study might affect research, practice or policy These findings suggest that reliance on a single diagnostic test may misclassify risk and that HbA1c may capture additional at-risk individuals in this population. They support the need for longitudinal studies and potential reconsideration of diagnostic thresholds or combined testing approaches tailored to specific populations.