Studies on glucose challenge test (GCT) as a screening procedure for gestational diabetes mellitus

A glucose challenge test (GCT) was developed as a screening procedure for the diagnosis of gestational diabetes mellitus (GDM). The method includes a 50gm oral glucose load and measurement of the plasma glucose concentration once at one hour after ingestion. The data were examined in 1,184 pregnant women seen at the outpatient clinic of our department from May 1984 to December 1986. Prior to the present study, 722 pregnant women were given a 75gm glucose tolerance test (75gGTT) and plasma glucose and IRI values were also analyzed. 1) Because glucose tolerance evaluated by the GCT was revealed to be impaired around the 28th week of pregnancy, it seems appropriate that screening for GDM should be planned during this period whenever possible. 2) The mean values obtained with GCTs performed before and after 28 weeks were 119 +/- 25mg/dl and 128 +/- 25mg/dl, respectively. 3) When the one-hour plasma glucose levels were compared after one 50 and one 75gm glucose load at intervals of less than 2 weeks, there was reproducibility in individual women with normal glucose tolerance, while the results were consistent in patients with DM or GDM. A mean difference of 18mg/dl at one hour was shown between the different glucose loads. 4) When screening for GDM was attempted in pregnant women with the 75gGTT, sensitivity and specificity were highest in the plasma glucose level at the one hour point. 5) GDM was found in the group of patients with plasma glucose levels of 155mg/dl or higher determined by GCT; the incidence was high in patients with plasma glucose levels of 160mg/dl or higher.(ABSTRACT TRUNCATED AT 250 WORDS)