BACKGROUND: Characteristics that identify patients who respond differently to certain interventions are called treatment effect modifiers. Some studies inappropriately report the presence of treatment effect modifiers without adequate study designs.
OBJECTIVE: To evaluate what proportion of single-group studies published in leading physical therapy journals inappropriately report treatment effect modifiers, and to assess whether the proportion varies over time or between journals.
METHODS: A systematic review was conducted of studies published in eight leading physical therapy journals since 2000. Eligible studies were single-group studies (e.g., cohort study or secondary analysis of treatment arm of randomised controlled trial) that investigated any condition, treatment or outcome. Studies that suggested participants with certain baseline characteristics responded better/or worse to the treatment, were considered to have reported inappropriately. Studies reporting that participants with certain baseline characteristics had improved outcomes but did not state it was due to the treatment were considered to have reported appropriately. The proportion of inappropriate reporting was compared over time and between journals.
RESULTS: Of the 145 included studies, 73 (50.3%) were categorised as inappropriately reporting treatment effect modifiers. The proportion of inappropriate reporting was highest in the most recent period, 2018 - 2022 (59.6%) and 2006 - 2011 (55.6%). The proportion of inappropriate reporting varied substantially between journals from 0% (Journal of Physiotherapy) to 91.7% (Journal of Neurologic Physical Therapy).
CONCLUSIONS: A large proportion (50.3%) of single-arm studies in leading physical therapy journals inappropriately report treatment effect modifiers. This inappropriate reporting risks misleading clinicians when selecting interventions for individual patients.

To assess markers of selection bias risk in a sample of recently published cluster randomized controlled trials compared with individually randomized trials.
We used OVID Medline and the online archives of the Journal of the American Medical Association to search for cluster randomized trials published between January 2015 and June 2017 from four high-impact journals and compared them to a matched sample of individually randomized trials.
We identified 23 cluster trials: 57% (n = 13) described a robust allocation method and 17% (n = 4) recruited all participants before randomization. Four (17%), eight (35%), and 11 (48%) were classified as at low, medium, and high bias risk, respectively. Meta-analysis showed significant age imbalance (-0.05, 95% CI = -0.057 to -0.043, I2 = 93.2%) in cluster trials, while the matched individually randomized trials showed no imbalance (0.005, 95% CI = -0.026 to 0.035, I2 = 0%). Cluster trials finding a statistically significant outcome in their primary measure showed a larger age imbalance (0.082, 95% CI = -0.091 to -0.073, I2 = 87%) than trials finding a nonstatistically significant outcome (0.022, 95% CI = 0.008 to 0.035, I2 = 83%).
There is strong evidence in this sample of an effect of selection bias seen in an imbalance in baseline participant age, something not seen in a comparable sample of individually randomized trials.

BACKGROUND: Recent studies have shown a decrease in annualised relapse rates (ARRs) in placebo groups of randomised controlled trials (RCTs) in relapsing multiple sclerosis (RMS).
METHODS: We conducted a systematic literature search of RCTs in RMS. Data on eligibility criteria and baseline characteristics were extracted and tested for significant trends over time. A meta-regression was conducted to estimate their contribution to the decrease of trial ARRs over time.
RESULTS: We identified 56 studies. Patient age at baseline (p < 0.001), mean duration of multiple sclerosis (MS) at baseline (p = 0.048), size of treatment groups (p = 0.003), Oxford Quality Scale scores (p = 0.021), and the number of eligibility criteria (p<0.001) increased significantly, whereas pre-trial ARR (p = 0.001), the time span over which pre-trial ARR was calculated (p < 0.001), and the duration of placebo-controlled follow-up (p = 0.006) decreased significantly over time. In meta-regression of trial placebo ARR, the temporal trend was found to be insignificant, with major factors explaining the variation: pre-trial ARR, the number of years used to calculate pre-trial ARR and study duration.
CONCLUSIONS: The observed decline in trial ARRs may result from decreasing pre-trial ARRs and a shorter time period over which pre-trial ARRs were calculated. Increasing patient age and duration of illness may also contribute.