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

Abstract

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.

Keywords: Gestational diabetes mellitus; Glucose challenge test; Glycated Hb; Screening.