Type of publication:
Conference abstract
Author(s):
*Basavaraju N.; *Al-Samaraaie E.; *Moulik P.
Citation:
Diabetic Medicine. Conference: Diabetes UK Professional Conference 2024. London . 41(Supplement 1) (no pagination), 2024. Date of Publication: 01 Apr 2024.
Abstract:
Introduction: HbA1c is a useful measure of glycaemic control over the preceding 3 months with an emphasis on preceding 30 days. We present four clinical scenarios that affect its reliability. Case 1: Twenty-nine-year-old female started on Dapsone for hidradenitis suppurativa. Pre-dapsone HbA1c was 38 mmol/mol and 2 years post-dapsone HbA1c <18 mmol/mol, normal fructosamine 272 mumol/L (211-328), glucose-6-phosphate dehydrogenase (G6PD) activity 12.9 IU/gHb (8.8-12.8), methaemoglobin 8.6% (0-1.5) and reticulocyte 6.5% (0.5-2.5) indicating haemolysis. Case 2: Forty-nine-year-old female with type 1 diabetes and rheumatoid arthritis started on sulfasalazine. HbA1c dropped from 65 to 30 mmol/mol, fructosamine 415 mumol/L (211-328), mildly raised reticulocyte 2.6%, haemoglobin 128 g/L (115-165) indicating mild haemolysis. Case 3: Fifty-nine-year-old male with type 2 diabetes and genetic haemochromatosis (C282Y homozygous) started venesection. HbA1c prior was 63 mmol/mol reduced to 29 mmol/mol, fructosamine 262 mumol/L and c-peptide 2760 pmol/L indicate good beta cell reserve. Case 4: Seventy-year-old female with Graves' disease, post-radioiodine hypothyroidism, HbA1c <20 mmol/mol (was 41 mmol/mol 2 years ago) as part of annual hypertension screen. Fasting glucose 6.0 mmol/L, low haemoglobin 102 g/L, high reticulocytes 9.5%, direct antiglobulin Coombs test positive indicating low HbA1c due to autoimmune haemolytic anaemia. Discussion(s): HbA1c depends on glycation of red blood cells (RBC) and is proportional to ambient glucose concentrations. Conditions that affect RBC lifespan and turnover can alter HbA1c values. Dapsone causes oxidative haemolysis as can sulfasalazine. Venesection and haemolytic anaemia shorten life span of red blood cells and duration of haemoglobin exposed to glucose in the bloodstream resulting in falsely lower HbA1c. Conclusion(s): Clinicians must be aware of conditions affecting accuracy of HbA1c and consider alternate tests including venous glucose, fructosamine, capillary glucose or continuous glucose monitoring.
DOI: 10.1111/dme.15296
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