Screening for Gestational Diabetes Mellitus by Measuring Glycated Hemoglobin Can Reduce the Use of the Glucose Challenge Test

BACKGROUND: Physiological changes during pregnancy, such as dilutional anemia and a reduced half-life of red blood cells, have prevented the use of glycated Hb (HbA(1c)) as a biomarker for gestational diabetes mellitus (GDM). Nevertheless, increasing evidence supports the use of HbA(1c) in GDM diagnostic strategies.We studied HbA(1c) as a biomarker of GDM and its possible use as a screening test to avoid the use of the glucose challenge test (GCT). METHODS: This case-control study involved 607 pregnant women between the 24th and 28th week of gestation. HbA(1c) level was determined, and GDM was diagnosed according to the National Diabetes Data Group criteria. The area under the ROC curve (AUC) was determined; two low and two high cut-off points were established to rule out GDM and classify high-risk pregnant women, respectively. For each cut-off, sensitivity (S), specificity (SP), and total number and percentage of GCTs avoided were determined. RESULTS: The AUC for HbA(1c) diagnostic performance was 0.68 (95% confidence interval 0.57–0.79). Using 4.6% HbA(1c) (27 mmol/mol) as the lower cut-off (S=100%), 14% of participants could avoid the GCT. Using 5.5% HbA(1c) (36 mmol/mol) as the upper cut-off (SP =94.5%), 6% of participants would be considered at high risk. CONCLUSIONS: HbA(1c) can be used as a screening test prior to the GCT, thereby reducing the need for the GCT among pregnant women at a low risk of GDM.