Hb A2-Calderdale [δ2(NA2)His→Asn; HBD: c.7C>A] and Misdiagnosis of Type 2 Diabetes Mellitus Due to Interference with Hb A1c When Using Cation Exchange High Performance Liquid Chromatography: A Case Report.

The Hb A2-Calderdale variant [δ2(NA2)His→Asn, HBD: c.7C>A] was described as a novel variant in 2014. However, a high performance liquid chromatography (HPLC) peak was never identified indicating that this fraction could be 'hiding' somewhere else in the chromatogram. In this case report, we present evidence that the physiochemical properties of Hb A2-Calderdale resemble those of Hb A1c, resulting in a coelution in variant mode on the Tosoh G8 but not the Tosoh G11. This coelution results in an overestimation of Hb A1c and can potentially cause misdiagnosis of type 2 diabetes mellitus (T2DM).