Question:
Is random plasma glucose an efficient screening test for abnormal
glucose tolerance in pregnancy?
Answer:
Random plasma glucose was determined in 276 apparently healthy pregnant
women attending our antenatal clinic at 28 to 32 weeks gestation. Mean
and standard deviation values within 2 h and greater than 2 h after a
meal were calculated. A standard 75-g oral glucose tolerance test was
then given to 250 of the 276 pregnant women. Three patients were found
to be diabetic and 46 had post-load concentrations indicative of
impaired glucose tolerance according to the criteria of the World
Health Organization (1980). Using a cut-off point whereby 15% of the
population would be tested, we would have identified only 2 of the 3
diabetics and 12 of the 46 with impaired glucose tolerance. This poor
predictive power cannot be resolved by altering cut-off points for
screening, or by altering the criteria for abnormal glucose tolerance.
The basic problem is lack of a close relation between 2-h glucose
tolerance value and random glucose when this has been taken greater
than 120 min after a meal. In this population with a high prevalence of
abnormal glucose tolerance, random plasma glucose is not an efficient
screening test.
