- Hemoglobin A1c (HbA1c) missed the majority of diabetes mellitus (DM) cases identified by oral glucose tolerance test (OGTT), particularly among racial/ethnic minorities.
Why this matters
- HbA1c is the preferred way to assess prevalence of glucose tolerance states, but underestimation of prevalence can affect screening guidelines and policy.
- Compared prevalence of glucose tolerance states based on HbA1c and OGTT fasting plasma glucose (FPG) and 2-hour post-challenged plasma glucose (2hPG) in 9000 adults (≥20 years) from the 2005-2014 National Health and Nutrition Examination Survey.
- 73.07% of DM cases defined by OGTT (FPG≥126 mg/dL or 2hPG≥200 mg/dL) were misclassified as normal with HbA1c.
- Includes 69.29% of missed cases among Mexican Americans, 80.26% among other Hispanics, 78.89% among non-Hispanic whites, and 58.65% among non-Hispanic blacks.
- Compared with OGTT, HbA1c sensitivity was 26.93% and specificity 93.39%.
- Sensitivity was 30.71% for Mexican Americans, 19.74% for other Hispanics, 21.11% for non-Hispanic whites, and 41.35% for blacks.
- HbA1c for normal glucose tolerance had a sensitivity of 84.91% and a specificity of 43.53%.
- Only 57.52% of those identified with normal glucose tolerance by HbA1c were likewise identified as normal with OGTT.