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Letters |15 April 1995

Prophylaxis for Stress-Related Gastric Hemorrhage

Jeffrey N. Martin

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TO THE EDITOR:
In their article on the prophylaxis of stress-related gastric hemorrhage, Ben-Menachem and coworkers [1] discuss several potential explanations for their finding of lack of efficacy of either cimetidine or sucralfate. Although alluded to in the discussion, the study's low statistical power deserves further elaboration.
The determination that 160 patients would be required in each treatment arm to provide 80% power to detect a 75% reduction in bleeding from a baseline rate of 12% is statistically correct [2]. A 75% reduction, however, may be overly optimistic for sample size calculations. Using the concepts of Goodman and Berlin [3] and basing calculations on an expected 75% reduction, it can be shown before the trial that any observed reduction in bleeding would have a predicted precision of about ±52%. In other words, even if the trial had found no (0%) reduction in bleeding, the study would not have statistically excluded up to a 52% reduction in bleeding. The use of a 75% reduction as the projected effect in sample size calculations severely diminished the study's ability to detect smaller effects that were still clinically relevant. Most clinicians would agree that if an agent reduced bleeding by 50%, or even by 30% to 40%, it would still be useful.
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Martin JN. Prophylaxis for Stress-Related Gastric Hemorrhage. Ann Intern Med. ;122:632–634. doi: 10.7326/0003-4819-122-8-199504150-00024

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Published: Ann Intern Med. 1995;122(8):632-634.

DOI: 10.7326/0003-4819-122-8-199504150-00024

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Print ISSN: 0003-4819 | Online ISSN: 1539-3704

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