What is "quality of evidence" and why is it important to clinicians?

doi:10.1136/bmj.39490.551019.BE

BMJ 2008;336:995-998 (3 May), doi:10.1136/bmj.39490.551019.BE

Analysis

Rating quality of evidence and strength of recommendations

What is "quality of evidence" and why is it important to clinicians?

Gordon H Guyatt, professor¹, Andrew D Oxman, researcher², Regina Kunz, associate professor³, Gunn E Vist, researcher², Yngve Falck-Ytter, assistant professor⁴, Holger J Schünemann, associate professor⁵, for the GRADE Working Group

¹ Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada L8N 3Z5, ² Norwegian Knowledge Centre for the Health Services, PO Box 7004, St Olavs plass, 0130 Oslo, Norway, ³ Basel Institute of Clinical Epidemiology, University Hospital Basel, Hebelstrasse 10, 4031 Basel, Switzerland, ⁴ Division of Gastroenterology, Case Medical Center, Case Western Reserve University, Cleveland, OH 44106, USA, ⁵ Department of Epidemiology, CLARITY Research Group, Italian National Cancer Institute Regina Elena, Rome, Italy

Correspondence to: G H Guyatt, CLARITY Research Group, Department of Clinical Epidemiology & Biostatistics, Room 2C12, 1200 Main Street West Hamilton, ON, Canada L8N 3Z5 guyatt@mcmaster.ca

Guideline developers use a bewildering variety of systems torate the quality of the evidence underlying their recommendations.Some are facile, some confused, and others sophisticated butcomplex

The first 150 words of the full text of this article appear below.

In 2004 the Grading of Recommendations Assessment, Developmentand Evaluation (GRADE) Working Group presented its initial proposalfor patient management.¹ In this second of a series of fivearticles focusing on the GRADE approach to developing and presentingrecommendations we show how GRADE has built on previous systemsto create a highly structured, transparent, and informativesystem for rating quality of evidence.

A guideline’s formulation should includea clear question with specification of all outcomes of importanceto patients

GRADE offers four levels of evidence quality: high,moderate, low, and very low

Randomised trials begin as highquality evidence and observational studies as low quality evidence

Qualitymay be downgraded as a result of limitations in study designor implementation, imprecision of estimates (wide confidenceintervals), variability in results, indirectness of evidence,or publication bias

Quality may be upgraded because of a verylarge magnitude of effect, a dose-response gradient, . . . [Full text of this article]

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