Interference in HbA1c measurement: a case of electropherogram shift due to hyperleukocytosis leading to the discovery of leukemic mantle cell lymphoma

HbA1c is a pivotal biomarker in diabetes management, reflecting long-term glycaemic control. HbA1c is often measured with capillary electrophoresis, which generally is a very precise technique, but there can be interference, especially in the case of haemoglobin diseases. Thus, in patients with underlying conditions, the accurate measurement of HbA1c can be challenging. We present a case of special interference in a 74-year-old female patient referred to a HbA1c test, in whom the measurement was thought to be significantly affected by hyperleukocytosis and led to an unexpected diagnosis of leukemic low-grade lymphoma. This case report highlights the underrecognized potential interference of leukocytosis in HbA1c measurement. It underscores the importance of clinical vigilance when interpreting HbA1c results in patients with underlying haematological conditions.