Impact of Time since Last Meal on the False Positive Result of 50 grams Glucose Challenge Test in the Pregnancy with Gestational Diabetes Mellitus Risk: A prospective cohort study

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Suphawan Pattamathamakul
Srisuda Songthamwat
Ueamporn Summart
Angkana Hansri
Metha Songthamwat


Objectives: To study the impact of time since last meal to the rate of false positive 50 grams glucose challenge test (GCT) during pregnancy with gestational diabetes mellitus (GDM) risk.
Materials and Methods: This prospective observational study was conducted in a tertiary care from December 2019 to August 2020. The participants were the singleton who had risks of GDM. The screening test was done using 50 grams GCT and then 100 grams oral glucose tolerance test (OGTT) used for diagnosis of GDM if GCT was ≥ 140 mg/dL. The participants’ information, time and type of last meal, time of 50 grams glucose intake and blood drawing, result of GCT and OGTT were recorded. The time since last meal was categorized to < 1, < 2 and < 3 hours. Bivariate and multivariable regression analysis were applied to evaluate the effect of time since last meal to GCT.
Results: There were 426 pregnant women completed study: 30.75% had positive GCT and 19% of these were diagnosis for GDM. The time since last meal < 1, < 2, and < 3 hours group had 36.0, 29.8, and 25.8 % false-positive CGT compared with 20.8, 18.2, 20.3% of ≥ 1, ≥ 2, and ≥ 3 hours group. The adjusted risk ratio (95% confidence interval) were 1.60 (1.14-2.24), 1.53 (1.06-2.22) and 1.23 (0.75-2.04) and p value were 0.006, 0.023, and 0.397, respectively.
Conclusion: The interval between the last meal and GCT less than 2 hours significantly increased a false positive rate of the test.


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