Harm outcomes applicable for most meta-analyses of randomized trials of biomedical interventions: a key concept in clinical epidemiology

Randomized trials are used to evaluate health care interventions because they minimize confounding and selection bias through randomization. Harms reporting in trials remain suboptimal, despite established guidelines. To improve transparency and clinical relevance, trialists should share information about harms-whether assessed systematically or nonsystematically. Nonsystematically assessed adverse events warrant greater attention, as they are often underreported or inconsistently documented. Trialists should specify what was measured, when, and by whom. For each study arm, tables or data should be available that include all harms observed. For dichotomous outcomes, tables or data should include the number of people who experienced each harm in each group: the number of participants at risk of harms (ie, randomized individuals); the number of deaths; participants with one or more adverse events; withdrawals (discontinuations) due to harms; and the total number of events, if appropriate. Thresholds should not be used to limit the sharing of information about harms. Zero events should be included for harms systematically assessed. For combined adverse events, such as the proportion of participants with one or more serious adverse events, researchers should report or share data for all component events (eg, deaths, major cardiovascular events, cancers, infections, and psychiatric events). Better harms reporting could improve evidence synthesis, enhance interpretability, and support informed clinical decision-making as well as patient safety.