Influence of food intake on the predictive value of the gestational diabetes mellitus screening test.

Objective: To investigate the influence of prior food ingestion on the predictive value of a screening test for gestational diabetes mellitus.

Methods: This prospective, nonrandomized study enrolled 1,387 pregnant women who underwent the 50-g glucose challenge test. Gestational diabetes mellitus was diagnosed according to the National Diabetes Data Group criteria. A nutritional survey of dietary information before the glucose challenge test was conducted. The patients were stratified into three groups based on the time of last food ingestion (fasting interval): 1 hour or less, 1-2 hours, and more than 2 hours. The more than 2-hours fasting interval group was defined as the "fasting" group, and the combined 1 hour or less and 1-2 hours fasting interval groups were defined as the "fed" group. We calculated the positivity rate and the positive predictive value to detect the predictive value.

Results: Among women who fasted 1 hour or less, 1-2 hours, and more than 2 hours before a glucose challenge test, 2.5%, 3.1%, and 6.9% were diagnosed with gestational diabetes mellitus, respectively. The positive predictive value of the glucose challenge test was greater in the fasting group than in the fed group (27.1% compared with 13.7%, P=.003). A multinomial logistic analysis showed that gestational diabetes mellitus was more prevalent in the fasting group than in the fed group (adjusted odds ratio 2.86, 95% confidence interval 1.65-4.95).

Conclusion: Our findings suggest that food intake influences the predictive value of the gestational diabetes screening test.

Level Of Evidence: II.