A collaboration of academic physical therapists in the USA independently reviewed the quality of clinical trials published by physiotherapy journals (Riley et al 2021).

Specifically, they examined the presence of post-randomisation bias in the randomised trials published by physiotherapy journals between 2016 and 2020.

Consistency in prospective registration

In that review, Journal of Physiotherapy was the only journal to have all randomised trials prospectively registered.

Furthermore, all of the trials showed complete consistency between the published study and its registered protocol.

Why does this matter for clinical physiotherapists and researchers?

Enforcement of prospective registration of study protocols by a journal prevents authors from selectively reporting the study’s outcomes.

In other words, the authors must report all the outcomes that they originally planned to measure.

This gives a fair picture of the intervention’s effects, unbiased by whether the result on a particular outcome is beneficial or not.

An independent appraisal of physiotherapy journals rated Journal of Physiotherapy highly on measures including prospective registration of randomised trials and external and internal validity. 

Without this system of checking, authors could get away with selecting only certain outcomes to report; for example, they could report only those outcomes that show favourable effects of the intervention and not report those showing adverse effects.

With such selective outcome reporting, readers would unwittingly get an unduly favourable impression of the effectiveness of the intervention.

Given the consistent results for Journal of Physiotherapy in the independent appraisal by Riley et al, clinical physiotherapists can be confident that the trials it publishes report all the outcomes listed in the original study protocol.

External and internal validity

In the review by Riley et al, Journal of Physiotherapy always reported the information required to establish the external validity of each trial.

Journal of Orthopaedic & Sports Physical Therapy and Journal of Physiotherapy received the highest internal validity scores—just below 8 on the PEDro scale.

Why does this matter for clinical physiotherapists and researchers?

Information about the external validity of a trial establishes the sort of patients to whom the results are applicable.

Readers of Journal of Physiotherapy can know that this information will always be included in the report of a clinical trial.

High internal validity scores are also important because this indicates that the study used methods to prevent sources of potential bias from affecting the estimates of treatment effects generated by the study.

This makes the study results more believable and therefore more applicable to clinical practice.

Reference

Riley, S.P., Swanson, B.T., Shaffer, S.M., Sawyer, S.F. & Cleland, J.A. ‘The unknown prevalence of postrandomization bias in 15 physical therapy journals: a methods review.’ J Orthop Sports Phys Ther 2021 Nov; 51(11): 542–550.