Comparison between 100-g glucose tolerance test and two other screening tests for gestational diabetes: combined fasting glucose with risk factors and 50-g glucose tolerance test.

Context And Objective: Lack of consensus about which screening tests to use for gestational diabetes mellitus (GDM) and difficulties in performing the gold-standard diagnostic test, the 100-g glucose tolerance test (100-g GTT), justify comparison with alternatives. The aim was to compare this with two other screening tests: combined fasting glucose with risk factors (FG + RF) and 50-g GTT.

Design And Setting: Prospective longitudinal cohort study in the Hospital School of Universidade Federal de Mato Grosso do Sul.

Methods: The three tests were performed independently on 341 pregnant women. Sensitivity (S), specificity (Sp), positive (PPV) and negative (NPV) predictive values, positive (PLR) and negative (NLR) likelihood ratios, and false-positive (FP) and false-negative (FR) rates obtained with FG + RF and 50-g GTT were compared with values from 100-g GTT. The average one-hour post-intake glucose levels (1hPG) with 50-g and 100-g were compared. Students t test was used in the statistical analysis.

Results: FG + RF led more pregnant women (53.9%) to diagnostic confirmation than did 50-g GTT (14.4%). The tests were equivalent for S (86.4 and 76.9%), PPV (98.7 and 98.9%), NLR (0.3 and 0.27) and FR (15.4 and 23.1%). Average 1hPG values were similar: 50-g GTT = 106.8 mg/dl and 100-g GTT = 107.5 mg/dl.

Conclusion: Diagnostic efficiency with simplicity, practicality and low cost make FG + RF more appropriate for screening for GDM. The equivalence of 1hPG allows a new, cheaper and less uncomfortable protocol to be proposed for screening and diagnosing GDM.