There are different definitions of a guideline. The most used and accepted definition is the one provided by the National Academy of Medicine (formerly Institute of Medicine) of the United States, which states that clinical practice guidelines (CPG) are statements that include recommendations, intended to optimise patient care, that are informed by a systematic review of evidence and an assessment of the benefits and harms of alternative care options". The development of these recommendations is reached by a consensus of a representative panel of experts in that area (screened for conflicts of interest), informed by analysis of the best available evidence*. In topic areas in which the scientific literature is weak or insufficient, and therefore will not support meta-analyses or network meta-analyses, evidence-informed and consensus-based guidelines have been developed employing the Trustworthy Consensus-Based Statement process (TCBS). One pillar of the TCBS requires an expert panel representing multiple stakeholder perspectives, screened for conflicts of interest (Lewis et al. 2014). Guideline producers incorporate explicit consideration of clinical effectiveness; cost and economic implications; ethical, social, cultural and legal issues; organisational and environmental aspects; as well as wider implications for the patient, relative, caregivers and the population. Evidence-based guidelines are increasingly being developed in areas beyond clinical practice, for example in public health and social care.

* Historically, many organisations have categorized their guidelines as evidence-based or consensus-based. However, both types of guidelines require a consensus among the committee members to take a decision on what to recommend for improving health outcomes. Thus, we suggest not using the distinction of consensus-based vs evidence-based guidelines, as long as the process and decisions made are informed by a comprehensive and systematic review of the evidence.