[When HbA1c is unreliable : a case report of hereditary spherocytosis]

Glycated haemoglobin (HbA1c) is a biological parameter used in the management of diabetic patients. Independent of the daytime glycaemic variations, but complementary to the measurement of blood glucose or subcutaneous glucose concentrations, it allows both the clinician and the patient to have an appreciation of the glycaemic balance of the last weeks. In this way, anti-diabetic treatment can be adjusted if necessary to achieve the desired goal and hopefully delay or prevent diabetes-related micro- and macroangiopathic complications. Some conditions can alter the glycation of haemoglobin. In this case, the HbA1c level becomes difficult to interpret. Hereditary spherocytosis may be revealed by a dissociation between low HbA1c level and high blood glucose levels. A family history, Coombs-negative haemolytic anaemia, or a finding of spherocytes in the blood smear is suggestive of hereditary spherocytosis. Fructosamine testing may be an alternative. This article will present a patient with hereditary spherocytosis in whom the HbA1c level was not interpretable when compared to the elevated blood glucose measurements.