The insulin test: negative and positive tests versus numerical values.

The result of the insulin test is commonly expressed as negative or positive according to different criteria. In 42 male duodenal ulcer patients subjected to selective vagotomy and pyloroplasty (SV + PP), negative and positive tests according to different criteria were compared with respect to the acid response to insulin and 2-deoxy-D-glucose (2DG), and to the percentage reduction of the response to insulin by SV + PP. The mean response to insulin and 2DG was smaller, and the mean reduction greater in negative than in positive tests according to any criterion. There was, however, a considerable over-lapping of the responses, or reductions, or both, between negative and positive tests. In tests negative to 4 or more criteria, insulin and 2 DG stimulated secretion by less than 0.50 mEq/30 min, but the reduction varied from 60 to 100 per cent. Accordingly, in individual patients the terms negative and positive test to most single criteria give no information about the acid response after the vagotomy nor about the effect of the vagotomy, unless the test is negative to 4 or more criteria. It is suggested that the result of the insulin or 2DG test should be reported in numerical values as basal and stimulated acid output and concentration instead of stating that the test is negative or positive.