Determination of Normal HbA1C Levels in Non-Diabetic Patients with Hemoglobin E

Hemoglobin E (Hb E) possesses an influence on HbA1c levels. Careful interpretation of HbA1c is needed in areas with a high prevalence of Hb E, including Thailand. Therefore, the normal levels of HbA1c in non-diabetic Hb E subjects were collected and assessed.

A cross-sectional study was conducted in Hb E subjects aged 18 years and above (N=70). An oral glucose tolerance test was performed. HbA1c levels were measured with 3 assays: ion exchange HPLC, immunoassay (ImmA), and enzymatic assay (EnzA). Individuals who received regular blood transfusions and diabetic patients were excluded.

Among 34 subjects with heterozygous Hb E (EA), the mean (±SD) HbA1c levels by HPLC, ImmA, and EnzA were 5.63±0.55%, 4.73±0.62%, and 5.29±0.37%, respectively. Among 29 subjects with homozygous Hb E (EE), the mean (±SD) HbA1c levels by HPLC, ImmA, and EnzA were 3.37±0.69%, 4.37±0.76, and 4.91±0.28%, respectively. Immunoassay and enzymatic methods seem preferable over HPLC for this population. The HbA1c level of 5.7 (99^th percentile) from immunoassay is a proposed cut-off point for detecting individuals who are at an increased risk of diabetes.

There are subjects with hemoglobin E whose HbA1c levels are deemed inaccurate due to the techniques used. Within this study normal HbA1c levels were determined by 3 different assays. The HbA1c level of 5.7 by immunoassay (Advia, 1600) is proposed as the cut-off point for diagnosing subjects at risk of diabetes.