To the Editor.

The recent publication by the PREVENT Study Group¹ requires clarifications for readers attempting to determine the place of this new Food and Drug Administration-approved therapy for select infants with increased risk of respiratory syncytial virus (RSV)-associated hospital morbidity. The first issue requiring comment relates to the presentation of results. Differences in hospital outcome with treatment versus control therapy are presented most frequently by the authors as percent improvement (attributed risk percent) rather than absolute risk difference when the authors wish to emphasize the beneficial effects of RespiGam (RSV-IGIV). For example, "infants and children at high risk for severe RSV disease who received monthly RSV-IGIV prophylaxis had a significant reduction in the incidence (41%) and total days (53%) of RSV hospitalization." Presenting the data as percent improvement may exaggerate the actual effect magnitude of an intervention. For example, if a disease outcome were to be reduced from 2 in 1 000 000 to 1 in 1 000 000 or 50 in 100 to 25 in 100, a 50% reduction would have occurred in both examples. However, the epidemiologic impact is considerably different in these two examples that have the same percent change in outcome. A more informative presentation would have been the attributed risk difference. For 100 RSV-IGIV monthly prophylaxed infants, there was observed a reduction of 5.5 hospitalizations (13.5% to 8.0%) and 69 fewer hospital days (129 to 60).

A second comment concerns the authors' failure to place in context . . . [Full Text of this Article]