We read with interest the article entitled “Use of hemoglobin A1C as an early predictor of gestational diabetes,” an interesting concept. Hemoglobin A1C (HbA1C), although suspected and considered as another modality of identifying gestational diabetes mellitus for >3 decades, has not been used as a screening tool for gestational diabetes mellitus. In 1 series, elevated HbA1C at the time of screening patients for gestational diabetes mellitus was predictive of macrosomia (>95 percentile) in 50% of patients with gestational diabetes mellitus. HbA1C was measured by cation column chromatography, and the finding of patients with variant hemoglobin was taken into consideration for more accurate interpretation. Fong et al mentioned that their patient population was predominantly Hispanic; however, these are the very patients who have high likelihood of variant hemoglobin. HbA1C, when measured by cation column chromatography, is lower in patients with variant hemoglobin (such as S or C) and higher in those with thalassemia. HbA1C values are affected by a number of other factors such as anemia, variant hemoglobin and hypertriglyceridemia, and uremia; thus, these results should be interpreted keeping this information in mind. Furthermore, HbA1C norms are lower in all trimesters of pregnancy. It would be interesting if Fong et al would address this issue of macrosomia (>90th percentile) in their patients with elevated HbA1C level and method of HbA1C measurement in their patients.

If there was no macrosomia, then this finding may be attributed to the early diagnosis that resulted in earlier and better glycemic control or that the cut of value of HbA1C used was very low and hence detection of diabetes mellitus was 27%.

Unfortunately, no plasma glucose levels were available at the time of initial glycohemoglobin level that was used for screening.

Although an attractive proposition, HbA1C for early prediction of gestational diabetes mellitus, should be used with due consideration to various factors enumerated.