Poor reliability of the first meal tolerance test.

ABSTRACT

The poor reproducibility of oral glucose tolerance test (OGTT) has been known for a long time. Some recent reports indicate that postprandial glycaemia achieved during the test is likely to be higher on the first occasion than on subsequent visits. We have analysed our recent data on meal tolerance tests (MTT) from this angle. Fifteen healthy subjects and 9 subjects having NIDDM were administered two essentially identical meals one or two weeks apart. In case of healthy subjects, the absolute as well as incremental postprandial glycaemia achieved at 0.5 h and 1.0 h on the first visit was significantly higher (P < 0.05) than on the subsequent visit. The effect of visit was insignificant in case of NIDDM subjects. The effect observed in healthy subjects may be due to the release of adrenaline during the first visit brought about by apprehension. In NIDDM subjects the apprehension is likely to be much less because of their having undergone such tests in the past. Hence a single casual OGTT or MTT is unreliable as a diagnostic tool in borderline cases of impaired glucose tolerance test. The test needs to be repeated at least once more to eliminate false positives.