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

ObjectiveThe 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 DesignBased 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).ResultsOf 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).ConclusionUnless maternal fasting glucose samples are transported on ice and analyzed immediately in the laboratory, gestational diabetes mellitus will be underdiagnosed in obese women.