In this meta-analysis and meta-regression, Ralf Watzlawick and colleagues determined the impact of study characteristics, methodologic and reporting bias, and the quality of neurologic recovery after experimental spinal cord injury (SCI) in a large cohort of 9,535 animals.
Overall, the included studies reported a neurobehavioral outcome improvement of 26.3%. However, the authors found that using multiple outcome measures was consistently associated with smaller effect sizes compared with studies applying only 1 outcome measure. More than half of the studies (51.2%) did not report blinded assessment, constituting a likely source of evaluation bias. Assessment of publication bias, which extrapolates to identify likely missing data, suggested that between 2% and 41% of experiments remain unpublished.
In summary, this study provides empirical evidence of prevalent bias in the design and reporting of experimental SCI studies, resulting in overestimation of the effectiveness. Bias compromises the internal validity and jeopardizes the successful translation of SCI therapies from the bench to bedside.