A Case of Variant Hemoglobin HbC in a Non-Diabetic Subject Treated With Anti-Diabetic Drugs Due to Falsely High HbA1c Levels Measured By an Immunoassay

Abstract

We herein describe a case of variant hemoglobin HbC in a non-diabetic subject treated with anti-diabetic drugs due to falsely high HbA1c levels measured by an immunoassay. A 29-year-old male was found to have a high HbA1c level (8.0 %) at his health check-up, and his doctor began administering anti-diabetic drugs. We measured his HbA1c using high-pressure liquid chromatography [HPLC; standard mode (SM) and variant mode (VM) ], an immunoassay and enzymatic assay to determine the cause behind the falsely high HbA1c levels. The HbA1c levels measured by both HPLC (VM) and an enzymatic assay were within the reference range, while those measured by HPLC (SM) were falsely low (3.8-4.2 %). The immunoassay was performed using five reagent kits, and the findings for HbA1c levels measured by two kits were falsely high while those measured by three kits were within the reference range. On investigation, we determined that the higher HbA1c levels measured by the immunoassay were due to the two kits using an antibody that recognizes the area containing a mutated sixth amino acid on the hemoglobin β chain, which led to increased antigenicity of the variant hemoglobin.