[Effect of hemoglobin N Baltimore on HbA1c measurement in six methods]

The presence of hemoglobin variants can adversely affect the accuracy of some HbA1c methods depending on the variant. We examine the analytical interference from a rare Hb variant (Hb N Baltimore) with six different HbA1c methods using various method principles: two immunoassays methods (Tina-quant^® HbA1c Gen et DCA Vantage), three high-performance liquid chromatography methods (G8 HPLC, Variant II Turbo A1c 2.0 et Variant II Dual kit), and one capillary-electrophoresis method (Capillarys Hb A1c kit). Hb N Baltimore can adversely affect determination of HbA1c levels. An underestimation of HbA1c level is observed with the chromatographic methods included in this study and no HbA1c result can be obtained with the capillary-electrophoresis method. Inversely, limited impact is observed with the immunoassays methods. The presence of an hemoglobin variant should be suspected when inconsistencies are observed between a patient's home blood glucose monitoring and laboratory-measured HbA1c. In these situations additional testing should be carried out using a test based on a different analytical method.