What HbA1c levels are predictive of type 2 diabetes mellitus (DM)?

Updated: Sep 27, 2021
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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Lu et al found evidence that a screening HbA1c of 5.5% or below predicts the absence of type 2 diabetes, while an HbA1c of 7% or greater predicts its presence, and levels of 6.5-6.9% indicate a high probability that diabetes is present. The investigators derived these cutoffs from a clinical group of 2494 patients, 34.6% of whom had undiagnosed diabetes, and then evaluated the cutoffs in a population-based sample of 6015 patients, 4.6% of whom had undiagnosed diabetes.

In the population-based group, HbA1c at 5.5% had a sensitivity of 83.5%, while HbA1c at 7% had a specificity of 100%. In both groups, many (61.9-69.3%) individuals with HbA1c levels of 5.6-6.9% had an abnormal glucose status. [156]

A community-based study by Lerner et al of 10,201 patients not previously diagnosed with diabetes found that patients whose baseline HbA1c levels were at 5.5% or higher but less than 6.5% had an increased risk of developing diabetes over the subsequent 5-8 years. Moreover, the risk of developing diabetes doubled with every increase of 0.5% in HbA1c level. The risk of diabetes was not associated with age or low socioeconomic status in this study. [157, 158]

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