The role of preanalytical glycolysis in the diagnosis of gestational diabetes mellitus in obese women

OBJECTIVE: The objective of this prospective observational study was to determine whether the preanalytical management of maternal plasma glucose samples had a significant effect on glucose measurements in obese pregnant women. STUDY DESIGN: Based on the accurate calculation of body mass index in the first trimester, obese women were recruited at their convenience. In 1 cohort, fasting glucose level was measured in early pregnancy; in the other cohort, an oral glucose tolerance test was performed at 24-28 weeks' gestation. Paired samples were taken from all women in both cohorts. The first sample was transferred to the laboratory in iced water for immediate analysis (fast-tracked analysis). The second sample was not placed on ice and transferred according to established hospital practices (hospital-tracked analysis). RESULTS: Of the 24 women who had a fasting glucose test in early pregnancy, the result was abnormal (≥5.1 mmol/L) in 7 women (29%) with hospital-tracked analysis compared with 16 women (67%) with fast-tracked analysis (P < .01). The mean phlebotomy-analysis interval was 119 minutes for the hospital-tracked samples compared with 23 minutes for the fast-tracked samples (P < .001). Of the 24 women who had a glucose tolerance test, the fasting glucose level was abnormal in 4 women (17%) after hospital-tracked analysis compared with 13 women (54%) after fast-tracked analysis (P < .01). The hospital-tracked phlebotomy-analysis interval for the fasting sample of the 24-28 week oral glucose tolerance test cohort was 166 minutes compared with 25 minutes for the fast-tracked samples (P < .001). CONCLUSION: Unless maternal fasting glucose samples are transported on ice and analyzed immediately in the laboratory, gestational diabetes mellitus will be underdiagnosed in obese women.