Quality of a body of evidence

The quality of a body of evidence refers to the degree to which the available evidence supports a particular conclusion or decision. In general, high-quality evidence is considered to be more reliable and trustworthy than low-quality evidence.

Several factors can affect the quality of evidence, including the design of the study, the size and representativeness of the study sample, the accuracy and precision of the measurements used, the level of bias and confounding, and the consistency of the findings across different studies.

The hierarchy of evidence-based medicine is often used to classify the quality of evidence, with systematic reviews and meta-analysis of randomized controlled trials (RCTs) generally considered to provide the highest-quality evidence, followed by individual RCTs, observational studies, and expert opinion. However, the quality of evidence can also depend on the specific context and the specific question being asked.

The GRADE approach is a system for rating the quality of a body of evidence in systematic reviews and other evidence syntheses, such as health technology assessments, and guidelines and grading recommendations in health care. GRADE offers a transparent and structured process for developing and presenting evidence summaries and for carrying out the steps involved in developing recommendations. It can be used to develop clinical practice guidelines (CPG) and other health care recommendations (e.g. in public health, health policy and systems and coverage decisions).