Levels of evidence

Evidence class is a term evidence-based medicine, which describes the form and content quality of a clinical trial and categorized. It describes a hierarchy of evidence.

A distinction is made according to the recommendations of the AHRQ ( Agency for Healthcare Research and Quality ), the evidence classes I to IV studies class Ia the highest level of evidence, studies in Class IV have the least. The higher the level of evidence, the better is the scientific justifiability for a derived therapeutic recommendation.

• Stage Ia: At least one meta-analysis on the basis of methodological quality of randomized controlled trials (RCTs )
• Stage Ib: at least a sufficiently large, methodologically high-quality RCT
• Stage IIa: at least one high-quality study without randomization
• Stage IIb: at least one high-quality study of a different type, quasi- experimental study
• Level III: more than a very qualitative non-experimental study such as comparative studies, correlation studies or case -control studies
• Level IV: Opinions and beliefs of respected authorities ( from clinical experience); Expert commissions; descriptive studies
• Level V: Case series or one or more experts opinions