The utility of HbA1c combined with haematocrit for early screening of gestational diabetes mellitus.

Aims: To evaluate the utility of glycated haemoglobin A1c (HbA1c) alone and in combination with haematocrit (HCT) for screening gestational diabetes mellitus (GDM) between 12-16 gestational weeks.

Methods: This prospective study was carried out in the Obstetrics and Gynaecology Hospital of Fudan University from November 2014 to February 2015. In total, 690 pregnant women between 20 and 35 years old were included in this study. All subjects received a routine blood examination for HbA1c and HCT at 12-16 gestational weeks (gw) and a 75-g oral glucose tolerance test at 24-28 gw. Threshold values for the diagnosis of GDM were a plasma glucose concentration of 5.1 mmol/L after fasting, 10.0 mmol/L at 60 min, and 8.5 mmol/L at 120 min. Receiver operating characteristic curves were used to evaluate the diagnostic performance of HbA1c with or without HCT.

Results: One hundred seven women were diagnosis with GDM at 24-28 gw. An HbA1c cutoff value < 4.55% at 12-16 gw showed adequate sensitivity to exclude GDM (85.0%) but low specificity (17.3%), while an HbA1c cutoff value ≥ 5.25% presented adequate specificity (96.6%) but low sensitivity (13.3%) in diagnosing GDM. The area under the receiver operating characteristic curve for HbA1c (12-16 gw) detection of GDM was 0.563 (95% confidence interval [CI], 0.50-0.625). When combined HbA1c with HCT ( > 38.8%) for the screening of GDM, the area under the receiver operating characteristic curve was 0.604 (95% [CI] 0.509, 0.701).

Conclusions: Whether the adoption of HbA1c as a screening test for GDM would benefit pregnant women remains to be determined. However, combining HbA1c with HCT for the screening of GDM may be a useful tool to predict GDM.