Drug-eluting stents
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* David J. Cohen
* Ameet Bakhai

*   © 2007 Canadian Medical Association or its licensors

Our interest in the systematic review by Suzanne Ligthart and colleagues of published studies evaluating the cost-effectiveness of drug-eluting stents1 was not dispassionate, as we are coauthors of 4 of the 19 published studies cited. We have several concerns about the analysis in this review.

The authors stipulated that each study included in the review had to be an “original cost-effectiveness analysis” and “from an unrestricted patient population.” We do not believe that any of our included studies meet these criteria. References 17 and 19 are review articles that briefly describe the results of models that were presented at scientific symposia. Neither of these papers was intended to fully convey the underlying methods or assumptions of the models. In fact, these 2 papers describe virtually the same cost-effectiveness analysis. References 20 and 29 describe prospectively conducted empirical cost-effectiveness analyses that were performed alongside the SIRIUS and TAXUS-IV trials, respectively. As noted in the published articles, each of these studies' conclusions apply only to the highly selected types of patients in the trials. It is well-recognized that only approximately 40% of current recipients of drug-eluting stents (and a smaller proportion of all patients with stents) meet the inclusion criteria for the SIRIUS and TAXUS-IV trials, and thus we do not believe that our conclusions constitute a recommendation for widespread use of drug-eluting stents.

Second, we are concerned about potential errors in determining the funding sources for the cost-effectiveness studies. In the case of our own studies, Ligthart and colleagues categorized reference 17 as being unfunded (the journal in which the paper was published did not request information on conflicts of interest) and they categorized reference 19 as being funded by industry (because 1 of the authors reported having received grant support from several manufacturers of drug-eluting stents). Reference 19 was directly solicited by the journal's editors and the cost-effectiveness analysis it describes was entirely unfunded. Ligthart and colleagues state that “studies were considered to be sponsored if the original publications indicated that funding was provided directly by the manufacturer of a drug-eluting stent.” Neither study meets this criterion. Had we been approached by the authors to clarify the funding sources for our studies, we would have been happy to provide the relevant details. Whether there were similar errors in categorizing other publications cited in the systemic review is unknown.

Third, we are concerned about the main outcome variable of the study: whether the conclusion of the study favoured widespread use of drug-eluting stents. The term “widespread” means different things to different people. Although Ligthart and colleagues were apparently able to reach consensus on this point, it is almost impossible to interpret the results of a study when the primary outcome measure is subjective and not well-defined. Given these 3 concerns and the small number of studies included in their sample, we suggest that the findings of Ligthart and colleagues may have several alternative interpretations beyond the ones they proposed.

## REFERENCE

1.  1. Ligthart S, Vlemmix F, Dendukuri N, et al. The cost-effectiveness of drug-eluting stents: a systematic review. CMAJ 2007;176(2):199-205.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czo5OiIxNzYvMi8xOTkiO3M6NDoiYXRvbSI7czoyNDoiL2NtYWovMTc2LzExLzE2MTIuMS5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=)