Interventions:
The authors justified their selection of placebo as the comparator for Xeomin, as no other botulinum neurotoxin type A preparation had been approved by the Scottish Medicine Consortium. Thus, the selection of the comparators appears to have been appropriate.
Effectiveness/benefits:
The relevant sources of evidence were selected without a literature review, because a detailed search had recently been performed as part of a Cochrane Review. Limited information on the characteristics of the clinical sources was provided, reducing the possibility of judging the validity of the clinical inputs. Another botulinum neurotoxin type A, namely Dysport, was used as a proxy for the utility changes attributable to Xeomin treatment. The authors stated that the same efficacy and toxicity profile was found for Dysport and Botox, and for Xeomin and Botox, allowing the interchangeable use of data between treatments. The clinical analysis comparing Xeomin and placebo was based on indirect comparison data and some assumptions were required, which introduced further uncertainty. The authors pointed out that QALYs were an appropriate benefit measure given the impact of the disease on a patient's quality of life. A validated instrument was used to elicit the patient preferences for health conditions, but a small sample of German patients was studied.
Costs:
The economic analysis was appropriately carried out and presented. The unit costs and resource quantities were reported. The price year was not clearly stated and this limits the possibility of performing reflation exercises for other time periods. The sources for the unit costs reflected the UK setting. Some estimates of resource consumption were based on expert opinion. The dosages were varied in the sensitivity analysis.
Analysis and results:
The expected costs and benefits were clearly presented and were appropriately synthesised in an incremental analysis. The uncertainty was only partly investigated and the methods were not clearly reported, but a deterministic one-way analysis appears to have been carried out. The authors stated that this was the first cost-effectiveness analysis comparing a botulinum neurotoxin type A with placebo, which makes this a useful study. They acknowledged some limitations that related to the low quality of some of the clinical data, the need for an indirect comparison and several assumptions, and the transferability of the utility values to the UK context.
Concluding remarks:
The methods were valid, but several assumptions were needed. Further studies are required to corroborate the authors’ findings.