Objectives: To compare the quality of randomized controlled trials (RCTs) published in predatory and nonpredatory journals in the field of physical therapy.

Data sources: From a list of 18 journals included either on Beall's list (n=9) or in the Directory of Open Access Journals (DOAJ) (n=9), 2 independent assessors extracted all the RCTs published between 2014 and 2017. When journals published more than 40 RCTs, a sample of 40 trials was randomly extracted, preserving the proportions among years. Indexing in PubMed, country of journal publication, and dates of submission or acceptance were also recorded for each journal.

Main outcome measures: The PEDro (Physiotherapy Evidence Database) scale and duration of the peer review.

Results: Four hundred ten RCTs were included. The mean PEDro score of articles published in non-Beall, DOAJ journals was higher than those published in Beall journals (mean score ± SD, 5.8±1.7 vs 4.5±1.5; P<.001), with the differences increasing when the indexing in PubMed was also considered (6.5±1.5 vs 4.4±1.5; P<.001). The peer review duration was significantly longer in non-Beall than in Beall journals (mean duration [d] ± SD, 145.2±92.9 vs 45.4±38.8; P<.001) and in journals indexed in PubMed than in nonindexed journals (136.6±100.7 vs 60.4±55.7; P<.001). Indexing in PubMed was the strongest independent variable associated with the PEDro score (adjusted R²=0.182), but noninclusion on Beall's list explained an additional, albeit small, portion of the PEDro score variance (cumulative adjusted R²=0.214).

Conclusions: Potentially predatory journals publish lower-quality trials and have a shorter peer review process than non-Beall journals included in the DOAJ database.