Diagnostic ability of elevated 1-h glucose challenge test

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To determine whether a threshold of a 1-h glucose challenge test (GCT) eliminates the need for a 3-h glucose tolerance test (GTT).


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.


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.


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.

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