To the Editor.—

The study by Pennesi et al was impressive in scope—spanning 7 centers and nearly 8 years—but had several limitations that threaten the validity of its findings and the certainty with which we can dismiss the role of antibiotic prophylaxis outright. First, the study sample was very small and had power to show only large differences in recurrent pyelonephritis rates. Given their sample size and observed 30% rate of recurrent pyelonephritis in the “no-prophylaxis” group, the recurrent pyelonephritis rate in children receiving antibiotic prophylaxis would had to have been <6.6% for the study to detect a statistically significant effect with 80% power. The study was not powered to detect smaller clinically significant reductions in recurrent pyelonephritis or to perform subgroup analyses to identify groups of children for whom prophylactic antibiotics might have been effective.

Second, we have serious concerns about the validity of the urine cultures...

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