Low HbA1c levels in a poorly controlled diabetic

Answers on p 421. A 52 year old man was referred to the diabetic clinic because of weight loss and persistent osmotic symptoms. He was diagnosed three years before presentation and was on diet therapy. His general practitioner was concerned that he had a “sinister cause” for his symptoms because his glycated haemoglobin (HbA1c) levels were “near normal” when repeated on several occasions (measured using the Menarini high performance liquid chromatography method, with a reference range of 4%–6%). He was in remission from Hodgkin’s disease. Initial clinical examination was unremarkable. Laboratory data were: haemoglobin 155 g/l, white cell count 4.81 × 1012/l (normal differential count), platelet count 214 × 109/l; liver enzymes, renal function, and microalbuminuria screen were normal. Other results are shown in table 1. Laboratory data Laboratory data What do the data demonstrate? What is the differential diagnosis and what would you do next? What is the pathophysiological basis of the discrepancies observed and how would you assess this man’s long term glycaemic control?