Objective: Although it has been suggested for over a decade that the methodological quality of trials should be assessed blinded, only recently some scientific evidence has been provided that blinding leads to lower and more consistent scores than open assessment. Our objective was to evaluate the effect of blinding on the methodological quality assessment of randomised controlled trials on the efficacy of nonsteroidal antiinflammatory drugs (NSAIIDs) for low back pain.

Methods: We compared the results of the open quality assessment of a previously conducted systematic review on the efficacy of NSAIDs for low back pain with the results of the blinded quality assessment for the update of this review for the Cochrane Collaboration. The methodological quality of 26 randomised controlled trials was independently assessed by two reviewers. A consensus method was used to solve disagreements and a third reviewer was consulted if disagreement persisted. The quality assessment for the Cochrane review was blinded for authors, institution and journal; acknowledgements were also deleted. The methodological quality was assessed by using a criteria list which has been used in several systematic reviews on therapeutic interventions for low back pain by our research group. The list consists of 16 criteria referring to various aspects of study population, description of interventions, outcome measurements and data presentation and analysis. The three criteria that are considered to be the most important by the Cochrane Collaboration, i.e., randomisation, double-blinding and description of withdrawals and drop-outs, are included.

Results: Results will be presented at the Cochrane Colloquium.