Interventions:
Details of the two interventions, including their dosage, were adequately reported. NSAIDs represented the current practice in the treatment of AS in the UK, while ETN was a potential treatment option for those failing on NSAIDs.
Effectiveness/benefits:
The estimates of the initial response to treatment were obtained from a RCT which should have a high degree of internal validity. However, it should be noted that 12% of the patients in the placebo arm of the trial received something other than NSAIDs - the stated comparator - which may have introduced bias into the results. The authors noted that the data on long-term disease progression were scarce, and therefore they relied on a cross-sectional study, which has known limitations. However, this was mitigated to some extent by the sensitivity analysis conducted on the effectiveness estimates. The primary outcome measure was the QALY which was appropriate as it reflects the impact of the treatment on the length and quality of life of AS patients.
Costs:
The costs appeared to reflect the stated perspective. The details of the sources of the cost and resource use estimates were reported in full. However, only the total treatment costs associated with ETN were reported in the paper, which will limit the possibility of replicating these results for other settings. In addition, no details of the unit or total costs for the comparator were reported. Further, the price year was not reported making it difficult to re-value the results in future years.
Analysis and results:
The authors conducted an appropriate incremental analysis and the full results were reported. The issue of uncertainty was adequately addressed through a sensitivity analysis, the results of which were discussed. The authors discussed the limitations of their model in detail.
Concluding remarks:
The methodology was generally satisfactory; however there were some limitations in the reporting, especially on the cost side. Nonetheless, the conclusions reached by the authors appear to be appropriate.