Background: The efficacy of using botulinum toxin A injections in cerebral palsy (CP) is controversial. The financial conflict of interest related to medical research can affect the conclusion of an evidence-based review. This study was performed to determine as to what proportion of studies on botulinum toxin A injections in patients with CP was sponsored by the industry and whether the assessments of botulinum toxin injection in CP were associated with industry support.
Methods: Studies were identified with a search of the PubMed database (January 1991 to November 2011). All prospective, comparative, English language studies on the use of botulinum toxin A injections in patients with CP were included. A total of 374 articles were screened, 128 potentially eligible full articles were retrieved, and 66 studies met our inclusion criteria. The funding sources of the articles were reviewed, and qualitative conclusions regarding the effect of botulinum toxin A injection were classified as being either favorable, neutral, or unfavorable.
Results: Of 66 eligible articles, 28 were funded by the industry, and 25 were not. The other 13 studies did not include information on the funding source. A significant association was observed between the funding source and qualitative conclusions (P=0.042). Fifteen (53.6%) of the 28 industry-sponsored studies had favorable conclusions, whereas only 5 (20%) of the 25 non-industry-sponsored studies had favorable conclusions.
Conclusions: About half of studies on the effect of botulinum toxin A in CP were sponsored by the industry. This systematic review revealed that the qualitative conclusions in those studies are more favorable to the use of the botulinum toxin A than the non-industry-sponsored studies. Clinicians should be aware of an industry-related conflict of interest regarding reports on the efficacy of botulinum toxin A injections in patients with CP.
Level of evidence: Level II-therapeutic study.