To the Editor.—
Shafer et al1 reported the usefulness of urine dipsticks for testing urine samples from males for microscopic pus, the presence of which correlates well with the presence of both Chlamydia trachomatis and Neisseria gonorrhoeae. These results are similar to our own published in 19882 but not mentioned by Shafer et al. We found that the 95% confidence interval for the sensitivity of the presence of leukocyte esterase was 78% to 100%; for the specificity it was 73% to 91%; and for the positive predictive value it was 34% to 72%. The results from Shafer et al for a comparable population—68%, 91%, and 49%, respectively—are remarkably close to our estimates. Ninety-five percent confidence intervals seem to be empirically relevant and should be taken seriously in interpretation of results.