Ann Lab Med 2019; 39(6): 524-529  https://doi.org/10.3343/alm.2019.39.6.524
Screening for Gestational Diabetes Mellitus by Measuring Glycated Hemoglobin Can Reduce the Use of the Glucose Challenge Test
Jose-Maria Maesa, Ph.D., Patricia Fernandez-Riejos, Ph.D., Concepcion Gonzalez-Rodriguez, M.D., and Victor Sanchez-Margalet, M.D.
Department of Clinical Biochemistry, Macarena University-Hospital, Seville, Spain
Corresponding author: Jose-Maria Maesa, Ph. D.
Department of Clinical Biochemistry, Macarena University-Hospital, Pascual de Gayangos 41, E, 2ºI, 41002, Seville, Spain
Tel: +34-666121496 Fax: +34-954907048 E-mail: jmaesam@gmail.com
Received: November 17, 2018; Revised: April 5, 2019; Accepted: June 11, 2019; Published online: November 1, 2019.
© Korean Society for Laboratory Medicine. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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 (HbA1c) as a biomarker for gestational diabetes mellitus (GDM). Nevertheless, increasing evidence supports the use of HbA1c in GDM diagnostic strategies.We studied HbA1c 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. HbA1c 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 HbA1c diagnostic performance was 0.68 (95% confidence interval 0.57–0.79). Using 4.6% HbA1c (27 mmol/mol) as the lower cut-off (S=100%), 14% of participants could avoid the GCT. Using 5.5% HbA1c (36 mmol/mol) as the upper cut-off (SP =94.5%), 6% of participants would be considered at high risk.
Conclusions: HbA1c 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, Glycated Hb, Glucose challenge test, Screening



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