Usefulness of the 50-g Glucose Challenge Test for Screening of Patients with Gestational Diabetes Mellitus and an Analysis of the Timing of Administration of the Test

Objective We determined whether performing the glucose challenge test (GCT) during early pregnancy is an effective screening method for gestational diabetes mellitus (GDM). Methods The subjects included 201 pregnant Japanese women on whom a GCT was performed in early and mid-pregnancy, and an oral glucose tolerance test (OGTT) was performed 2—3 weeks after the GCT. The cut-off level for GCT determination was set at 130 mg/dl. The results of the OGTT that indicated the GDM type were displayed as the "GDM pattern." The present study identified the cases as GDM only if they exhibited a GDM pattern based on the results of OGTT conducted during mid- pregnancy. Results Based on the results of the GCT with respect to GDM detection during mid-pregnancy, the sensitivity and specificity of the test were found to be 100% (3/3) and 88% (174/198), respectively. During early pregnancy, the sensitivity and specificity of GCT with respect to detection of cases exhibiting a GDM pattern in an OGTT were 63% (5/8) and 84% (63/193), respectively. The 3 cases that were diagnosed as GDM during mid-pregnancy were found to be GCT-positive during early preg- nancy, and a GDM pattern was observed based on the results of an OGTT that was conducted during early pregnancy. Thus, the sensitivity and specificity of GCT during early pregnancy for GDM-detec- tion during mid-pregnancy were 100% (3/3) and 84% (166/198), respectively. Discussion GCT performed during early pregnancy is an effective screening method for detecting GDM during mid-pregnancy.