Using fasting plasma glucose concentrations to screen for gestational diabetes mellitus: prospective population based study.

OBJECTIVE: To evaluate whether measuring fasting plasma glucose concentration is an easier screening procedure for gestational diabetes mellitus than the 1 hour 50 g glucose challenge test. DESIGN: Prospective population based study. SETTING: Outpatient clinic in a university hospital. PARTICIPANTS: 520 pregnant women (328 (63%) white, 99 (19%) Asian, 31 (6%) African, 62 (12%) others) with mean age 28.4 (SD 0.2; range 17-45) years. All underwent a glucose challenge test between the 24th and 28th gestational week, followed by a diagnostic 3 hour 100 g oral glucose tolerance test within one week. This was done irrespective of the result of the challenge test. MAIN OUTCOME MEASURE: Receiver operating curves were used to determine the best cut off values for screening with fasting plasma glucose concentrations. RESULTS: Fasting plasma glucose concentration at a threshold value of 4.8 mmol/l and the glucose challenge test with a threshold value of 7.8 mmol/l yielded sensitivities of 81% and 59% respectively and specificities of 76% and 91% respectively. Measuring fasting plasma glucose concentration as a screening procedure required a diagnostic test in 30%, compared with 14% when the challenge test was used. CONCLUSIONS: Measuring fasting plasma glucose concentrations using a cut off value of >/=4. 8 mmol/l is an easier screening procedure for gestational diabetes than the 50 g glucose challenge test and allows 70% of women to avoid the challenge test.