In response to Maher and colleagues' letter,1 we would like to point out that in our report,2 we made a general statement regarding psychometric properties of the quality assessment tools used in physical therapy, and we did not specifically state that the Physiotherapy Evidence Database (PEDro) scale has not been appropriately tested for validity or reliability. This statement was based on our previous review, which investigated the psychometric properties of tools to evaluate the quality of randomized controlled trials in health research and especially in physical therapy.3 The above-mentioned review highlighted that most of the existing scales to determine trial quality were not adequately developed, including the PEDro scale. According to the developers of the PEDro scale, the scale was developed based on the Delphi list.4 Based on our results,3 the Delphi list lacked internal consistency and construct validity. These psychometric properties are of importance in any scale because they indicate that the construct—in this case, “methodological quality” (or “risk of bias,” the more current term for this concept)—is fully …
