Endocrine Abstracts

Introduction: Glycated haemoglobin (HbA1c) is used to measure glycaemic control in patients with diabetes, and accuracy depends on normal erythrocyte lifespan. Dapsone causes spuriously low HbA1c results by reducing erythrocyte lifespan through haemolysis and methaemoglobin formation, which interferes with the liquid-chromatography method used to measure HbA1c. Dapsone-induced haemolysis (DIH) is mostly reported in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, but there are rare reports in patients with normal G6PD who have high Dapsone levels during renal dysfunction or concomitant use of medications that use the cytochrome P-450 isoenzyme system. We report a case of DIH and spuriously low HbA1c values in a woman with diabetes.

Case: A 56-year-old female presented a record of low HbA1c values indicating excellent diabetes control despite raised random capillary blood glucose (CBG) levels indicating otherwise. She had type 1 diabetes on insulin treatment, coeliac disease and erythema elevatum diutinum for which she took Dapsone (50−100 mg daily) since 2013. HbA1c results were above 53 mmol/mol for several years indicating inadequate diabetes control but then dropped (<25 mmol/mol) while on Dapsone.

Investigation and management: Serum haematinics were normal. Reticulocyte count was high while in Dapsone (>81.0×10⁹/l). Blood film demonstrated bite cells and red cell fragments suggestive of chronic low-grade DIH. Haemoglobinopathy and G6PD screens were normal. She had mild normocytic anaemia (110 g/l) with normal liver, thyroid and renal function. Simultaneous fructosamine and HbA1c values were 300 µmol/l and 19 mmol/mol, respectively (the estimated equivalent HbA1c value should be 50 mmol/mol). Therefore, CBG monitoring, subcutaneous sensors and fructosamine levels were used for monitoring diabetes control.

Conclusion: We have presented DIH and spuriously low HbA1c levels in a patient with diabetes that has normal G6PD levels and renal function. HbA1c monitoring in this group of patients is unreliable and other methods should be employed.