Evaluation of HbA(1c) determination methods in patients with hemoglobinopathies

OBJECTIVE - To evaluate commercially available determination methods for HbA(1c) in patients with hemoglobin variants. RESEARCH DESIGN AND METHODS - HbA(1c) values were determined with various commercially available methods, including ion-exchange high-performance liquid chromatography (HPLC), boronate affinity assay, and immunoagglutination in patients with the hemoglobin mutations Hb Graz, Hb Sherwood Forest, Hb O Padova, Hb D, and Hb S. RESULTS - The effect of hemoglobinopathies on glycohemoglobin measurements was highly method dependent. The HPLC methods for HbA(1c) determination lacked the resolution necessary to differentiate hemoglobin variants. They demonstrated additional peaks in the chromatograms and HbA(1c) results either too low or too high compared with the nondiabetic reference range. With all immunoassays, Hb Graz demonstrated falsely low values. The other hemoglobinopathies in our study caused falsely low and/or high HbA(1c) results in immunoagglutination methods. The boronate affinity method showed values in an acceptable range for all hemoglobin variants. CONCLUSIONS - Because of the local occurrence of Hb variants and the ethnic origin of a given population, every individual laboratory must establish and validate its own assay method. In managing diabetic patients, knowledge of hemoglobinopathies influencing HbA(1c) determination methods is essential because hemoglobin variants could cause mismanagement of diabetes resulting from false HbA(1c) determinations.