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Table 2 Details about methodological quality of included studies

From: Is PEEK cage better than titanium cage in anterior cervical discectomy and fusion surgery? A meta-analysis

Quality assessment for randomized trials Niu CC Chen Y Chou YC Cabraja M Quality assessment for non-randomized trials
Was the assigned treatment adequately concealed prior to allocation? 2 1 2 2 A clearly stated aim
Were the outcomes of participants who withdrew described and included in the analysis? 0 2 1 1 Inclusion of consecutive patients
Were the outcome assessors blinded to treatment status? 2 0 0 0 Prospective data collection
Were the treatment and control group comparable at entry? 2 2 1 2 Endpoints appropriate to the aim of the study
Were the participants blind to assignment status after allocation? 0 0 1 2 Unbiased assessment of the study endpoint
Were the treatment providers blind to assignment status? 0 0 2 2 A follow-up period appropriate to the aims of the study
Were care programmes, other than the trial options, identical? 2 2 2 2 Less than 5 % loss to follow-up
Were the inclusion and exclusion criteria clearly defined? 2 2 0 0 Prospective calculation of the sample size
Were the interventions clearly defined? 2 2 2 2 Prospective calculation of the sample size
Were the outcome measures used clearly defined? 2 2 1 2 An adequate control group
Were diagnostic tests used in outcome assessment clinically useful? 2 2 2 1 Baseline equivalence of groups
Was the surveillance active, and of clinically appropriate duration? 2 2 2 2 Adequate statistical analyses