Aberrantly high glycated haemoglobin measurement due to the haemoglobin variant Hb Santa Juana.

Various laboratory and patient-related factors can result in falsely high or low glycated haemoglobin (HbA1c) measurements, and haemoglobin (Hb) variants that interfere with laboratory readings is an important cause of this. We report a case of a rare Hb variant, Hb Santa Juana, manifesting as a falsely high HbA1c in a 62-year-old patient with type 2 diabetes mellitus. The patient presented with high HbA1c values that persisted despite the intensification of anti-diabetic treatment. His home blood glucose levels were incongruently low compared to his HbA1c values. Further investigations revealed a family history of the variant Hb Santa Juana. This was confirmed in the patient when his blood was sent for DNA analysis. It is important for clinicians to be aware of the factors that can influence laboratory HbA1c measurements, as clinical decisions on treatment are often based on these measurements.