Diagnostic ability of elevated 1-h glucose challenge test

Objective:to determine whether a threshold of a 1-h glucose challenge test (gct) eliminates the need for a 3-h glucose tolerance test (gtt).study design:a retrospective cohort of patients undergoing gtt after gct was ⩾140 mg dl−1. gestational diabetes mellitus (gdm) was diagnosed using national diabetes data group (nddg) and carpenter–coustan (cc) criteria. sensitivity, specificity and predictive values were calculated for 1-h gct values of 160 to 220 mg dl−1.result:of 6218 patients, 988 (15.9%) had an elevated gct and 753 (12.1%) underwent a gtt. in all, 165 (2.7%) were diagnosed with gdm using nddg criteria, and 250 (4.0%) by cc criteria. the positive predictive value of a 1-h of gct ⩾200 mg dl−1 for gdm was 68.6% by nddg and 80.0% for gdm by cc criteria.conclusion:although the predictive value of an elevated 1-h ⩽200 mg dl−1 for gdm was high, 1 in 3 to 1 in 5 women would be overdiagnosed with gdm if the 3-h gtt was omitted.