Haemoglobin Marseille-Long Island and interpretation of HbA1c: Which HbA1c result is the "right answer"?

Abstract

A woman was screened for diabetes using glycated haemoglobin (HbA1c). Vastly different results were obtained by high performance liquid chromatography (45%), immunoassay (2.9%), and affinity chromatography (4.2%) compared with the non-diabetic range of less than 6.4%. Mass spectral studies confirmed the presence a haemoglobin variant, haemoglobin Marseille-Long Island which had confounded interpretation by all methods.