Unexpected Detection of HbH-CS in a Pregnant Woman by Assessing HbA1c Using Capillary Electrophoresis

Testing for hemoglobin A1C (HbA1C) is useful for following up on glycemic control in diabetic patients as well as in pregnant women.

A pregnant Chinese woman appeared for regular pregnancy check-ups. While monitoring blood glucose, an HbA1c test was initially performed in the pregnant Chinese woman using a CE-HPLC assay and capillary electrophoresis. Then acid gel Hb electrophoresis, a reverse dot-blot (RDB) assay, gap-PCR and DNA sequencing were applied to further evaluate the Hb variants.

The CE-HPLC system has shown that the percentage of blood HbA1c was 5.4%, while hemoglobin electrophoresis of HbA2 and HbA0 were 1.6% and 88.7%, respectively. The capillary electrophoresis measurement results were 6.4% HbA1c, 0.4% HbA2, and 84.1% HbA0. HbA2 and HbA were 0.8% and 89.3%, respectively. Further gap-PCR, the reverse dot-blot (RDB) assay, and DNA sequencing showed that the pregnant woman had HbH-CS (αα CS/--) (1800 bp and 1300 bp) and β/β.

Our study demonstrates that hemoglobin variants, such as HbH-CS can affect capillary electrophoresis results. An HbH-CS diagnosis in a pregnant woman is clinically significant. Laboratories should be cautious in using the CE-HPLC assay to evaluate HbA1c results in the presence of hemoglobin variants. Our findings highlight the strong discriminatory power of capillary electrophoresis for various Hb variants.