When is HbA1c useful and what do the numbers mean – do they help or hinder?

Authors

  • Susan E Manley Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; College of Medical and Dental Sciences, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK; Green Templeton College, University of Oxford, Oxford, UK https://orcid.org/0000-0002-8298-4511
  • Samiul Mostafa Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; College of Medical and Dental Sciences, Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK; Diabetes Centre, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK https://orcid.org/0000-0002-0415-7908
  • Jonathan Webber Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Diabetes Centre, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  • Kavitha D Ganapathy City Hospitals, Birmingham, UK
  • Roy Taylor Magnetic Resonance Centre, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK https://orcid.org/0000-0001-6273-0170
  • Randie R Little Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri, USA https://orcid.org/0000-0001-6450-8012
  • Rajeev P Raghavan Diabetes Endocrine Services, Diabetes Endocrine Centre, Location C28, New Cross Hospital, Royal Wolverhampton Trust, Wednesfield Road, Wolverhampton, WV10 0QP, UK
  • Craig Webster Clinical Laboratory Services, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK https://orcid.org/0000-0001-6395-0503
  • Alison Barratt https://alisonbarratt.com/
  • Rachel A Round Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Clinical Laboratory Services, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  • Irene M Stratton Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; University of Oxford, Oxford UK; University of Southampton, Southampton, UK https://orcid.org/0000-0003-1172-7865
  • Andreas Karwath Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; MRC Health Data Research UK (HDR UK) Midlands, Birmingham UK; College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK; Institute of Translational Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK https://orcid.org/0000-0002-6942-3760
  • John A Williams Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK; Institute of Translational Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Mammalian Genetics Unit, Medical Research Council Harwell Institute, Harwell, UK; Eisai Inc, Cambridge, MA, USA https://orcid.org/0000-0002-0357-5454
  • Georgios V Gkoutos Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; MRC Health Data Research UK (HDR UK) Midlands, Birmingham UK; College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK; Institute of Translational Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; NIHR Experimental Cancer Medicine Centre, Birmingham, UK; NIHR Surgical Reconstruction and Microbiology Research Centre, Birmingham, UK; NIHR Biomedical Research Centre, Birmingham, UK; BHP Centre for Health Data Research, University of Birmingham, B15 2TT, UK https://orcid.org/0000-0002-2061-091X
  • Graham A Roberts Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Diabetes Research Unit (Cymru), Grove Building, Swansea University, Swansea, UK; HRB-Clinical Research Facility – University College Cork, Cork, Ireland; Department of Endocrinology and Diabetes, University Hospital Waterford, Waterford, Ireland https://orcid.org/0000-0002-5018-0391
  • Sandip Ghosh Diabetes Translational Research Group, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Department of Endocrinology, Zulekha Hospital Sharjah, UAE https://orcid.org/0000-0003-0333-5992

DOI:

https://doi.org/10.15277/bjd.2023.417

Keywords:

HbA1c, inpatient diagnosis, gestational diabetes, remission, red blood cells

Abstract

Background: Glycated haemoglobin (HbA1c) measurement is used for diagnosis, management and remission of type 2 diabetes (T2DM), with measurements comparable worldwide and the World Health Organization listing medical conditions that affect its accuracy. Admission glucose is in the ‘diabetes’ range in 5% of emergency hospital admissions without prior diagnosis, with literature searches indicating inconsistent practice on using HbA1c to confirm diagnosis. As oral glucose tolerance tests (OGTT) were not possible during the COVID-19 pandemic, guidance was issued by the Royal College of Obstetrics and Gynaecology on using HbA1c for gestational diabetes mellitus.

Aims: This study explores use of HbA1c at Queen Elizabeth Hospital Birmingham, a large university hospital serving a multi- ethnic adult population.

Methods: Information is presented on comparability, clinical audits, research studies and current practice, and is illustrated by case reports.

Results: Data from the National Glycohemoglobin Standardization Program show comparability of laboratoryHbA1c and point-of-care testing methods from 1993 to 2023. Although HbA1c was used to diagnose gestational diabetes during the COVID-19 pandemic, hospitals have reverted to OGTT post pandemic. In contrast, HbA1c is now being used to assess T2DM remission. Case reports illustrate these scenarios and highlight the complexity of decision-making when the accuracy of the HbA1c reading is affected by multiple co- morbidities.

Conclusions: This wider use of HbA1c includes remission of T2DM but the diagnosis of gestational diabetes has reverted to OGTT post pandemic. A pictorial representation of HbA1c range is presented to aid understanding of this test. It is suitable for diagnosis of diabetes in most people except those with some variant haemoglobins or abnormal red blood cell turnover.

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