Background and Objective: The expanding use of botulinum toxin (BoNT) in medical practice demonstrates the need to highlight whether there is adequate information regarding its safety profile. The aim of our study was to identify completeness of harms reporting for BoNT treatment within systematic reviews (SRs), assess quality of SRs using the AMSTAR-2 tool, and determine the degree of overlap among primary studies within each SR.
Methods: On May 31, 2022, we searched Embase, Epistemonikos, MEDLINE, and the Cochrane Database of Systematic Reviews for SRs on BoNT therapy. Screening and data extraction were performed in a masked, duplicate fashion. AMSTAR-2 was used to evaluate the methodological quality of included SRs. Corrected covered area (CCA) was calculated for SR dyads.
Results: Of the 90 included SRs, we found that 70 completed less than 50% of harms items. The most reported items were BoNT as a favorable intervention (73/90, 81.1%) and harms as a primary outcome (72/90, 80.0%). The least reported items were grades and severity scales used to classify harms (8/90, 8.9%) and number of treatment discontinuations in each arm (10/90, 11.1%). Eighty-three SRs were rated “critically low” (83/90, 92.2%), while 5 SRs were rated “high” (5/90, 5.6%) via AMSTAR-2 tool. Significant associations were found between completion of harms reporting and: (1) a “critically low” appraisal on AMSTAR-2 tool (p = 0.0060) and (2) whether harms was reported as a primary outcome (p = 0.0001). The total CCA overlap was determined to be 0.8%.
Conclusion: Our results demonstrate that harms are underreported within BoNT SRs. Because healthcare professionals often refer to SRs to guide clinical decision making, it is important to continue to explore shortcomings among BoNT literature in future studies.