title: [GRADE system: classification of quality of evidence and strength of recommendation].
abstract: The acquisition and classification of scientific evidence, and subsequent formulation of recommendations constitute the basis for the development of clinical practice guidelines. There are several systems for the classification of evidence and strength of recommendations; the most commonly used nowadays is the Grading of Recommendations, Assessment, Development and Evaluation system (GRADE). The GRADE system initially classifies the evidence into high or low, coming from experimental or observational studies; subsequently and following a series of considerations, the evidence is classified into high, moderate, low or very low. The strength of recommendations is based not only on the quality of the evidence, but also on a series of factors such as the risk/benefit balance, values and preferences of the patients and professionals, and the use of resources or costs.
authors.affiliation: Servicio de Cirugía General, Hospital General Universitario JM Morales Meseguer, Campus de Excelencia Internacional Mare Nostrum, Universidad de Murcia, Murcia, España.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Aguayo-Albasini
authors.affiliation: Servicio de Cirugía General, Hospital General Universitario JM Morales Meseguer, Campus de Excelencia Internacional Mare Nostrum, Universidad de Murcia, Murcia, España. Electronic address: florespastorbenito2@gmail.com.
authors.forename: Benito
authors.initials: B
authors.lastname: Flores-Pastor
authors.affiliation: Servicio de Cirugía General, Hospital General Universitario JM Morales Meseguer, Campus de Excelencia Internacional Mare Nostrum, Universidad de Murcia, Murcia, España.
authors.forename: Víctor
authors.initials: V
authors.lastname: Soria-Aledo
mesh_terms: D005069:Evaluation Studies as Topic; D019317:Evidence-Based Medicine / Q000145:classification; D006801:Humans; D017410:Practice Guidelines as Topic / Q000592:standards*
keywords: Calidad de la evidencia; Clinical Practice guidelines; Evidence quality; Fuerza de la recomendación; GRADE system; Guías de práctica clínica; Sistema GRADE; Strength of recommendation