Construct validity of the Physiotherapy Evidence Database (PEDRo) quality scale for randomized trials: Item Response Theory analyses.

Albanese, Emiliano; Bütikofer, Lukas; Armijo-Olivo, Susan; Ha, Christine; Egger, Matthias (2020). Construct validity of the Physiotherapy Evidence Database (PEDRo) quality scale for randomized trials: Item Response Theory analyses. Research Synthesis Methods, 11(2), pp. 227-36. Wiley 10.1002/jrsm.1385

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BACKGROUND There is agreement that the methodological quality of randomized trials should be assessed in systematic reviews, but debate on how this should be done. We conducted a construct validation study of the Physiotherapy Evidence Database (PEDro) scale, which is widely used to assess the quality of trials in physical therapy and rehabilitation. METHODS We analyzed 345 trials that were included in Cochrane reviews, and for which a PEDro summary score was available. We used one- and two-parameter logistic item response theory (IRT) models to study the psychometric properties of the PEDro scale, and assessed the items' difficulty and discrimination parameters. We ran goodness of fit post-estimations and examined the IRT unidimensionality assumption with a multidimensional IRT model (MIRT). RESULTS Out of a maximum of 10, the mean PEDro summary score was 5.46 (SD=1.51). The allocation concealment and intention-to-treat scale items contributed most of the information on the underlying construct (with discriminations of 1.79 and 2.05, respectively) at similar difficulties (0.63 and 0.65, respectively). The other items provided little additional information, and did not distinguish trials of different quality. There was substantial evidence of departure from the unidimensionality assumption, suggesting that the PEDro items relate to more than one latent trait. CONCLUSIONS Our findings question the construct validity of the PEDro scale to assess the methodological quality of clinical trials. PEDro summary scores should not be used; rather the physiotherapy community should consider working with the individual items of the scale.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Pre-clinic Human Medicine > CTU Bern
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM)

UniBE Contributor:

Bütikofer, Lukas and Egger, Matthias


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services






[4] Swiss National Science Foundation




Andrea Flükiger-Flückiger

Date Deposited:

22 Nov 2019 09:24

Last Modified:

10 Mar 2020 09:06

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

item response theory physiotherapy randomized clinical trials risk of bias study quality scale validation




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