[Precautions regarding the calculation and interpretation of relative risk in pediatric studies]

The presentation of the results of a clinical study, whether experimental or observational, commonly uses the relative risk (RR) and its 95% confidence interval. RR is defined as the ratio between the absolute risk of an event of interest in an exposed group and that in an unexposed group. Proper interpretation and calculation of this effect measure are essential for informed decision-making; therefore, pediatricians must understand certain methodological and mathematical precautions related to its calculation, which are often overlooked. This educational article aims to explain various considerations and precautions regarding the calculation and interpretation of RR in pediatric studies. Based on a real research study, it explains how RR is calculated and interpreted, and addresses key aspects such as the inherent asymmetry of its values and confidence interval, the need to calculate it within the context of prospective studies, the potential overestimation of the odds ratio (OR) compared to RR when calculated from the same data, the difference between relative and absolute effect measures, the variations in the magnitude and precision of the confidence interval of the RR when analyzing the opposite event, and the methodological differences between RR estimation based on cumulative incidence versus incidence density. The article concludes that understanding these methodological and mathematical considerations is essential for a rigorous interpretation of RR and sound decision-making.