Reproducibility of the oral glucose tolerance test in pregnant women.

Abstract

The purpose of this study was to evaluate the reproducibility of the 3-hour oral glucose tolerance test during pregnancy and the potential factors associated with nonreproducible results. Thirty-eight women with a 1-hour glucose level > or 135 mg/dl had a 100 gm oral glucose tolerance test. During the test samples were obtained for glucose, insulin, cortisol, human placental lactogen, and norepinephrine levels. The oral glucose tolerance test was repeated 1 week later under similar metabolic conditions. The intraassay coefficient of variation in glucose from week 1 to week 2 was < 2%. There were no significant differences in the paired fasting 1-, 2-, or 3-hour glucose concentrations (p = 0.51 to 0.96) or the area under the glucose curve (p = 0.43) from week 1 to week 2, although the mean absolute difference in glucose values ranged from 4 (fasting) to 18 (3 hours) mg/dl. Oral glucose tolerance test results were classified as either normal or abnormal from week 1 to week 2; 16 normal/normal, 13 abnormal/abnormal, seven abnormal/normal, and two normal/abnormal. Norepinephrine (p = 0.03) and insulin (p = 0.05) were significantly greater in week 1 but not in week 2 in the abnormal/normal versus normal/normal and abnormal/abnormal groups. There were no significant differences in cortisol or human placental lactogen levels among groups at any time. The oral glucose tolerance test was not reproducible for diagnosis in 24% (nine of 38) of pregnant women. We speculate that maternal stress (increased norepinephrine) may have been a factor for the abnormal results in week 1 in the abnormal/normal group.