Applicability of a Combination of Hemoglobin A1c and Fasting Plasma Glucose in Population-based Prediabetes Screening

Journal of Diabetes, 03/06/2012

The enhanced prevalence of prediabetes using HbA1c+FPG compared with FPG+2hPG calls for the need to redefine at a more basic and a more practical level how to apply HbA1c in screening for prediabetes. A redefined HbA1c that incorporates FPG, age, race/ethnicity and BMI may put forward a better way to use HbA1c in population–based and clinical settings.


  • Data (n=1376) from the 2007–2008 U.S. National Health and Nutrition Examination Surveys were used for this investigation.
  • Prediabetes cut points were determined using 5.7–6.4%, 100–125 mg/dl, and 140–199 mg/dl of HbA1c, FPG and 2hPG, respectively.
  • Concordances between HbA1c and FPG, HbA1c and 2hPG, HbA1c+FPG and FPG+2hPG in screening for undiagnosed prediabetes were determined using sensitivity, specificity, and positive and negative likelihood ratios.


  • The overall concordance between HbA1c+FPG and FPG+2hPG in screening for prediabetes was high as indicated by sensitivity of 92.4% [95% CI=90.5–94.5]) and specificity of 84.1% [95% CI=81.2–87.0].
  • The application of HbA1c+FPG was associated with higher prevalence of prediabetes compared to FPG+2hPG.
  • Compared with FPG+2hPG, screening with HbA1c+FPG was associated with 3.2%, 24.3% and 4.2%relative increased in identification of prediabetes in nondiabetic non–Hispanic Whites, non–Hispanic Blacks and Mexican–Americans, respectively.

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