Is HbA1c a good screening test for diabetes mellitus?

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Trefor N Higgins1, David Tran, George S Cembrowski

  • 1DynaLIFEDx, Edmonton, Alberta, Canada. Trefor.higgins@dynalifedx.com

Clinical Biochemistry
|September 22, 2011
PubMed

Insights

The optimal diagnostic threshold for Hemoglobin A1c (HbA1c) for diabetes is 7.0%, offering better accuracy than 6.5%. However, even at 7.0%, the positive predictive value remains suboptimal for diagnosing diabetes.

Area of Science:

  • Endocrinology
  • Clinical Diagnostics
  • Public Health

Background:

  • Hemoglobin A1c (HbA1c) is now a primary diagnostic tool for diabetes mellitus.
  • The diagnostic accuracy of HbA1c compared to the oral glucose tolerance test (OGTT) requires further evaluation.

Purpose of the Study:

  • To assess the positive predictive value (PPV) and negative predictive value (NPV) of HbA1c testing for diabetes diagnosis.
  • To compare the diagnostic performance of different HbA1c thresholds against the OGTT.

Main Methods:

  • Retrospective analysis of three years of concurrent HbA1c and OGTT data.
  • Calculation of PPV and NPV using receiver operator (ROC) curves at a 10% diabetes prevalence.

Main Results:

  • An HbA1c threshold of 7.0% yielded higher PPV (0.61-0.73) and acceptable NPV (0.91-0.92) compared to the recommended 6.5% threshold.
  • The 6.5% HbA1c threshold showed lower PPV (0.40-0.61) and slightly higher NPV (0.92-0.93).

Conclusions:

  • An HbA1c threshold of 7.0% is optimal for diabetes diagnosis, outperforming the 6.5% threshold.
  • Despite being optimal, the 7.0% HbA1c threshold has a suboptimal PPV, potentially leading to overdiagnosis in up to 12% of individuals.
Abstract

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