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Appraising the quality of randomized controlled trials: inter-rater reliability for the OTseeker evidence database


Dr Leigh Tooth
School of Population Health
University of Queensland
Mayne Medical School
Herston Road
QLD 4006


Rationale and aims  ‘OTseeker’ is an online database of randomized controlled trials (RCTs) and systematic reviews relevant to occupational therapy. RCTs are critically appraised and rated for quality using the ‘PEDro’ scale. We aimed to investigate the inter-rater reliability of the PEDro scale before and after revising rating guidelines.

Methods  In study 1, five raters scored 100 RCTs using the original PEDro scale guidelines. In study 2, two raters scored 40 different RCTs using revised guidelines. All RCTs were randomly selected from the OTseeker database. Reliability was calculated using Kappa and intraclass correlation coefficients [ICC (model 2,1)].

Results  Inter-rater reliability was ‘good to excellent’ in the first study (Kappas ≥  0.53; ICCs ≥  0.71). After revising the rating guidelines, the reliability levels were equivalent or higher to those previously obtained (Kappas ≥  0.53; ICCs ≥  0.89), except for the item, ‘groups similar at baseline’, which still had moderate reliability (Kappa = 0.53). In study 2, two PEDro scale items, which had their definitions revised, ‘less than 15% dropout’ and ‘point measures and variability’, showed higher reliability. In both studies,  the  PEDro  items  with  the  lowest  reliability  were  ‘groups similar at baseline’ (Kappas = 0.53), ‘less than 15% dropout’ (Kappas ≤  0.68) and ‘point measures and variability data’ (Kappas ≤  0.68).

Conclusion  The PEDro scale is a reliable instrument for rating the quality of RCTs. Revised rating guidelines are provided for scale items that are difficult to rate, and helped to improve inter-rater reliability.