Glycosylated hemoglobin (HbA1) and hemoglobinopathies in pregnancy

Glycosylated hemoglobin (HbA1) is considered to be representative of prior blood-glucose levels and is being used in pregnant and nonpregnant diabetic patients as a possible index of both long and short-term glucose-control. Factors other than blood-glucose concentration have been reported to affect its value. Variant hemoglobin is one of them. HbA1 and blood-glucose levels were measured in pregnant patients at high risk for diabetes for screening for abnormal carbohydrate metabolism. HbA1 was measured by cation exchange column chromatography and glucose was measured by hexokinase reaction. The mean HbA1 in patients with normal blood sugars was 6.17 +/- 0.6 percent. A value of HbA1 of less than 5 percent as measured by cation exchange column chromatography was highly predictive (P less than 0.001) of hemoglobinopathies (S or C). The mean HbA1 of randomly selected matched patients with "normal" Hb was 5.94 +/- 0.72 percent. In patients with thalassemia, HbA1 values as measured by cation exchange column chromatography were elevated despite normal carbohydrate tolerance. While interpreting the results of HbA1 in the management of pregnant diabetics, the above fact should be kept in mind.