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.