Pitfalls of HbA1cin the Diagnosis of Diabetes

Michael Bergman, Muhammad Abdul-Ghani, João Sérgio Neves, Mariana P. Monteiro, Jose Luiz Medina, Brenda Dorcely, Martin Buysschaert

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Many health care providers screen high-risk individuals exclusively with an HbA1c despite its insensitivity for detecting dysglycemia. The 2 cases presented describe the inherent caveats of interpreting HbA1c without performing an oral glucose tolerance test (OGTT). The first case reflects the risk of overdiagnosing type 2 diabetes (T2D) in an older African American male in whom HbA1c levels, although variable, were primarily in the mid-prediabetes range (5.7-6.4% [39-46 mmol/mol]) for many years although the initial OGTT demonstrated borderline impaired fasting glucose with a fasting plasma glucose of 102 mg/dL [5.7 mmol/L]) without evidence for impaired glucose tolerance (2-hour glucose ≥140-199 mg/dl ([7.8-11.1 mmol/L]). Because subsequent HbA1c levels were diagnostic of T2D (6.5%-6.6% [48-49 mmol/mol]), a second OGTT performed was normal. The second case illustrates the risk of underdiagnosing T2D in a male with HIV having normal HbA1c levels over many years who underwent an OGTT when mild prediabetes (HbA1c=5.7% [39 mmol/mol]) developed that was diagnostic of T2D. To avoid inadvertent mistreatment, it is therefore essential to perform an OGTT, despite its limitations, in high-risk individuals, particularly when glucose or fructosamine and HbA1c values are discordant. Innate differences in the relationship between fructosamine or fasting glucose to HbA1c are demonstrated by the glycation gap or hemoglobin glycation index.

Original languageEnglish (US)
Pages (from-to)2803-2811
Number of pages9
JournalJournal of Clinical Endocrinology and Metabolism
Issue number8
StatePublished - Aug 1 2020


  • HIV
  • HbA1c
  • OGTT
  • diabetes
  • fructosamine
  • prediabetes

ASJC Scopus subject areas

  • Biochemistry, medical
  • Endocrinology
  • Biochemistry
  • Clinical Biochemistry
  • Endocrinology, Diabetes and Metabolism


Dive into the research topics of 'Pitfalls of HbA1cin the Diagnosis of Diabetes'. Together they form a unique fingerprint.

Cite this