Falsely Decreased HbA1c in Diabetic Patient due to Dapsone

HbA1c and fructosamine are glycated proteins used to monitor glucose control over time in patients with diabetes. Many factors can affect HbA1c values leading to spuriously low or elevated results. We report a case of a 67 year old woman with type 1 diabetes with good glycaemic control based on HbA1c values ranging from 44-52 mmol/mol over 7 year follow-up. She was commenced on dapsone for treatment of granuloma anulare; four months into this treatment her HbA1c was 25 mmol/mol. The record of self-monitoring blood glucose showed that most of her glucose values were within the recommended target. She had normal hypoglycaemia awareness and reported only 3 episodes of symptomatic hypoglycaemia in the preceding four months. Given the history of dapsone therapy and the discordant result of self-monitoring blood glucose and HbA1c concentrations, we suspected methemoglobinemia as a cause. Dapsone treatment has been recognised to cause falsely low HbA1c results by two mechanisms: haemolysis by reducing the erythrocyte life span and the formation of methemoglobin which interferes with HPLC used to measure HbA1c. In conclusion, dapsone is commonly used in diabetic patients who have other autoimmune diseases. HbA1c monitoring in patients treated with dapsone is unreliable and other markers such as capillary blood glucose records, and other glycated proteins such as fructosamine should be used as an alternative for monitoring of glucose control is such patients. Disclosure K. Aljenaee: None. S. Haji Ali: None. A. Pazderska: None.