Background: The potential effect of increase in hemoglobin (Hb) A(2) and HbF on glycated hemoglobin (HbA(1c)) measurements were investigated using a high-performance liquid chromatography (HPLC) method compared with an immunoturbimetric assay.,Methods: Samples producing abnormal chromatograms during the measurement of routine HbA(1c) testing with HPLC were further analyzed to characterize abnormal Hb variants. Patients were divided into three groups that had only high HbF (group 1), only high HbA(2) (group 2), and both high HbA(2) and HbF (group 3). A(1c) values of patients were re-assayed using the immunoturbidimetric method (Advia, Siemens Healthcare, Germany).,Results: HbA(1c) levels were significantly higher in all groups measured by immunoassay than in HPLC. We found a positive correlation between I IPLC and immunoturbidimetry in the group 2 and a slight correlation in the group 1. There was no correlation between the two methods in group 3.,Conclusions: HbA(1c) measurement by HPLC method interfering with elevated HbA(2) and HbF, especially HbF, should be verified by an immunoturbidimetric method.