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HbA1c performs well in monitoring glucose control even in populations with high prevalence of medical conditions that may alter its reliability: the OPTIMAL observational multicenter study

  • Niwaha, Anxious J1, 2
  • Rodgers, Lauren R3
  • Greiner, Rosamund1
  • Balungi, Priscilla A1, 2
  • Mwebaze, Raymond4
  • McDonald, Timothy J1
  • Hattersley, Andrew T1
  • Shields, Beverley M1
  • Nyirenda, Moffat J2, 5
  • Jones, Angus G1
  • 1 University of Exeter, Exeter, UK , Exeter
  • 2 MRC/UVRI and LSHTM Uganda Research Unit, Entebbe, Uganda , Entebbe (Uganda)
  • 3 University of Exeter Medical School, Exeter, UK , Exeter
  • 4 St. Francis Hospital Nsambya, Kampala, Uganda , Kampala (Uganda)
  • 5 London School of Hygiene & Tropical Medicine, London, UK , London
Published Article
BMJ Open Diabetes Research & Care
Publication Date
Sep 17, 2021
DOI: 10.1136/bmjdrc-2021-002350
PMID: 34535465
PMCID: PMC8451306
PubMed Central
  • 1506
  • 1866


Introduction The utility of HbA1c (glycosylated hemoglobin) to estimate glycemic control in populations of African and other low-resource countries has been questioned because of high prevalence of other medical conditions that may affect its reliability. Using continuous glucose monitoring (CGM), we aimed to determine the comparative performance of HbA1c, fasting plasma glucose (FPG) (within 5 hours of a meal) and random non-fasting glucose (RPG) in assessing glycemic burden. Research design and methods We assessed the performance of HbA1c, FPG and RPG in comparison to CGM mean glucose in 192 Ugandan participants with type 2 diabetes. Analysis was undertaken in all participants, and in subgroups with and without medical conditions reported to affect HbA1c reliability. We then assessed the performance of FPG and RPG, and optimal thresholds, in comparison to HbA1c in participants without medical conditions thought to alter HbA1c reliability. Results 32.8% (63/192) of participants had medical conditions that may affect HbA1c reliability: anemia 9.4% (18/192), sickle cell trait and/or hemoglobin C (HbC) 22.4% (43/192), or renal impairment 6.3% (12/192). Despite high prevalence of medical conditions thought to affect HbA1c reliability, HbA1c had the strongest correlation with CGM measured glucose in day-to-day living (0.88, 95% CI 0.84 to 0.91), followed by FPG (0.82, 95% CI 0.76 to 0.86) and RPG (0.76, 95% CI 0.69 to 0.81). Among participants without conditions thought to affect HbA1c reliability, FPG and RPG had a similar diagnostic performance in identifying poor glycemic control defined by a range of HbA1c thresholds. FPG of ≥7.1 mmol/L and RPG of ≥10.5 mmol/L correctly identified 78.2% and 78.8%, respectively, of patients with an HbA1c of ≥7.0%. Conclusions HbA1c is the optimal test for monitoring glucose control even in low-income and middle-income countries where medical conditions that may alter its reliability are prevalent; FPG and RPG are valuable alternatives where HbA1c is not available.

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