In their recent report, Alappan and colleagues [1] do not state clearly whether theirs was a prospective clinical study or a concurrent or retrospective chart review project. If this was a prospective clinical study, no mention was made of approval by an institutional review board or of written informed consent by patients.

In their Methods section, the authors stated that "the charts of these patients were reviewed prospectively in the hospital." They further stated that

serum potassium, sodium, and chloride concentrations; serum carbon dioxide content; anion gap; blood urea nitrogen level; and serum creatinine level were measured and recorded daily before initiation of and during therapy with trimethoprim-sulfamethoxazole in both the treatment group and the control group.

This statement seems to suggest that the study was prospective, given that these measurements are not usually done daily in clinical practice. When one looks at the results, however, it becomes clear that these measurements were not done daily, as the authors claim. In their Figure 1, the authors showed that serum potassium values were available in only 68, 74, 69, 64, and 53 of the 80 patients on days 1 through 5, respectively. Similarly, serum potassium values were available in only 21, 24, 19, 16, and 13 of the 25 controls on days 1 through 5, respectively.

The study period was January 1994 to March 1995. Surely, more than 80 patients were given trimethoprim-sulfamethoxazole during that time. What was the total number treated? How many patients were excluded and for what reasons? Many patients must have received other antibiotics during that period. How were the 25 controls selected, and why were they selected over other patients? Why were only 25 controls chosen, rather than a number closer to that (n = 80) of the patients?

For the reader to critically evaluate an article, it is important that the authors state accurately and unambiguously what was not done, what was done, and how it was done.