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Table 1 Criteria for judgment risk of bias for each study

From: Evaluation of the prognostic impact of postoperative adjuvant radiotherapy on head and neck mucosal melanoma: a meta-analysis

Domains Judgment criteria for responses to each domain
Yes No Unclear
Selection bias    
Selection    
Any criteria descriptions for the patients Any different radiotherapy plan,tumor stage,local recurrence,distant metastasis,follow duration etc. Not mentioned  
The representativeness of the postoperative radiotherapy group truly representative of the average, elderly, community-dwelling resident somewhat or selected group of patients, e.g. only certain socio-economic groups/areas no description of the derivation of the cohort
The representativeness of the surgery only group drawn from the same community as the intervention cohort drawn from a different source no description of the derivation of the non intervention cohort
Comparability    
Group comparable for:a.average age b.negative margin c patinet status All the three variables were comparable between the groups at least one of these was not reported even if others were comparable Not mentioned
Group comparable for:a.tumor stite b.radiotherapy plan c.tumor stage All the three variables were comparable between the groups At least one of those was not comparable even if others were not reported Not mentioned
Control for confounding at each outcome Appropriate methods are used to control the potential confounders (e.g. matching, modeling, etc.) No method was applied to control the potential confounders Insufficient description
Design or Analysis bias    
Blinding of participants at each outcome 1.Blinding of participants at each outcome 1. No blinding or incomplete blinding, the outcome is likely to be influenced by lack of blinding Insufficient description
2.No blinding or incomplete blinding, but the reviewers judge that the outcome is not likely to be influenced by lack of blinding 2. Blinding of key study participants and likely that the blinding could been broken, and the outcome is likely to be influenced by lack of blinding
3. Blinding of key study participants and unlikely that the blinding could been broken
Ascertainment of intervention exposure Medical records or structured interview Written self report Insufficient description
Outcomes    
Blinding of outcome assessment at each outcome 1. Blinding of outcome assessment at each outcome 1. No blinding of outcome assessment, the outcome measurement is likely to be influenced by lack of blinding. Insufficient description
2. No blinding of outcome assessment, but the reviewers judge that the outcome measurement is not likely to be influenced by lack of blinding.
2. Blinding of outcome assessment ensured, and likely that the blinding could have been broken and the outcome assessment is likely to be influenced by lack of blinding.
3. Blinding of outcome assessment ensured, and unlikely that the blinding could have been broken.
Ascertainment of outcome data Record linkage Self report Insufficient description
Was follow up long enough for outcomes to occur The follow-up was long enough for outcomes to occur, if median duration of follow-up > = 6 month if median duration of follow-up < 6 months Insufficient description
Adequacy of follow up of cohorts 1. complete follow up: all subjects accounted for follow up rate < 80 % (select an adequate %) and no description of those lost Insufficient description
2. subjects lost to follow up unlikely to introduce bias: number lost < = 20 %, or description of those lost suggesting no different from those followed
  1. 1. Cochrane Handbook for Systematic Reviews of Interventions http://handbook.cochrane.org/. Accessed 2014 Dec 6
  2. 2. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses: http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed 2014 Dec 6