A Case With Falsely High HbA1c Value by a Probable Novel Mechanism of Hemoglobin Modification

Abstract

We experienced a case in which a novel hemoglobin modification mechanism was implicated in a falsely high HbA1c value. The patient was a 72-year-old man. He visited our department because his HbA1c value, as measured by high-performance liquid chromatography (HPLC) (HA-8180, Arkry Inc. ), was as high as 7.9 %. Although his fasting plasma glucose level was within the reference range, a 75 g oral glucose tolerance test showed a diabetic type result. His HbA1c did not decrease with guidance on lifestyle improvement and administration of antidiabetic drugs. Since the HbA1c value measured by enzymatic assay was 5.2 % in the medical examination, antidiabetic drugs were discontinued and detailed examinations were performed. The patient's HbA1c values measured by an enzymatic assay, immunoassay, and affinity assay, as well as his glycated albumin value and 1,5-anhydroglucitol value were all within the reference range. An analysis by high-resolution HPLC revealed an abnormal peak eluting earlier than HbA1c. However, variant hemoglobin was ruled out because no mutation was found in any of the globin genes. This case suggested the existence of a novel mechanism of hemoglobin modification.