Which level of evidence is considered the highest for an intervention question?

The highest level of evidence for an intervention question is represented by systematic reviews. This is because systematic reviews synthesize findings from multiple studies, evaluating the quality and results of each to provide a comprehensive overview of the evidence on a particular intervention. By aggregating data from various high-quality studies, these reviews aim to minimize bias and enhance reliability in the conclusions drawn.

Systematic reviews are typically seen as the gold standard, especially when they include meta-analyses, which quantitatively summarize data from the individual studies. This extensive and rigorous approach makes systematic reviews far more trustworthy than individual studies or expert opinions, as they encompass a broader scope of research and a greater diversity of populations and settings.

In contrast, while randomized controlled trials (RCTs) are also a high level of evidence, they are still individual studies. RCTs are designed to test an intervention's effectiveness in a controlled setting but do not provide the aggregated perspective that systematic reviews deliver. Controlled cohort studies and expert opinions rank lower on the hierarchy of evidence, as they may lack the rigor and comprehensive analysis found in systematic reviews.