A Pitfall in HbA1c Testing Caused by Hb Long Island Hemoglobin Variant

Although many factors may interfere with hemoglobin (Hb)A1c measurement, Hb variants are among the most important factors.

We tested the HbA1c levels of the patient, a 32 year old Manchu Chinese woman, during a routine health check. We used different methods, including high-performance liquid chromatography (HPLC) and capillary electrophoresis, to test specimens from the patient. Next, we tested the specimen further using polymerase chain reaction (PCR) and sequencing.

We discovered that our patient, who had an HbA1c value of 0, also has an Hb variant, Hb Long Island, which we found during the HbA1c analysis as part of her routine health check at the Health Management Center in the General Hospital of Tianjin Medical University, Tianjin, China. Also, we discovered that the exon 1 of β gene contained transversion mutations, with 1 heterozygous and 1 homozygous variant (HBB:c.8A > C, 9T > C). These gene mutations resulted in an amino-acid change (His to Pro) and a decrease in HbA1c value.

When there is no correlation between the clinical signs, glycemic status, and glycated Hb levels of the patient, the chromatogram of HbA1c should be carefully checked to detect possible variants that cause interference in the measurement.