Methodological quality and synthesis of case series and case reports

A pyramid has expressed the idea of hierarchy of medical evidence for so long, that not all evidence is the same. Systematic reviews and meta-analyses have been placed at the top of this pyramid for several good reasons. However, there are several counterarguments to this placement. We suggest another way of looking at the evidence-based medicine pyramid and explain how systematic reviews and meta-analyses are tools for consuming evidence—that is, appraising, synthesising and applying evidence.

Case reports and case series have their own role in the progress of medical science. They permit discovery of new diseases and unexpected effects (adverse or beneficial) as well as the study of mechanisms, and they play an important role in medical education. Case reports and series have a high sensitivity for detecting novelty and therefore remain one of the cornerstones of medical progress; they provide many new ideas in medicine. At the same time, good case reporting demands a clear focus to make explicit to the audience why a particular observation is important in the context of existing knowledge.

Trustworthy clinical practice guidelines should be based on a systematic review of the literature, provide ratings of the quality of evidence and the strength of recommendations, consider patient values, and be developed by a multidisciplinary panel of experts. The quality of evidence reflects our certainty that the evidence warrants a particular action. Transforming evidence into a decision requires consideration of the quality of evidence, balance of benefits and harms, patients' values, available resources, feasibility of the intervention, acceptability by stakeholders, and effect on health equity. Empirical evidence shows that adherence to guidelines improves patient outcomes; however, adherence to guidelines is variable. Therefore, guidelines require active dissemination and innovative implementation strategies.