Cost Effectiveness of Drug-Eluting Stents in Acute Myocardial Infarction Patients in Germany

Article excerpt

Key points for decision makers

* In a routine-care setting, the implantation of drug-eluting stents in acute myocardial infarction (AMI) patients appears to be not associated with any differences in 1-year survival rates compared with bare-metal stents while treatment costs are significantly higher

* From an economic point of view, drug-eluting stents do not seem to be a cost-effective technology for all AMI patients. However, they might be cost effective in certain patient subgroups

* The use of administrative data for cost-effectiveness analysis provides valuable information that complements data from clinical trials

Background

Ischaemic heart diseases (IHDs) are one of the major causes of death in Western countries. Among IHDs, acute myocardial infarction (AMI) is one of the most important diagnoses. AMI results from an occlusion within the coronary arteries, usually preceded by one or more stenoses of the coronary arteries. In Germany the incidence of AMI has increased from 169 165 cases in 2000 to 213 683 cases in 2007. At the same time, mortality has decreased substantially from 89.1 people per 100 000 inhabitants in 2000 to 75.4 people per 100 000 inhabitants in 2007.[1] The high number of patients has facilitated research and development activities in the area of IHD, resulting in innovative pharmaceuticals and medical devices.[2] The decline in AMI mortality that has also been observed in other Western countries has been mainly attributed to technological advance.[3]

For several years an increasingly large share of patients has received coronary stents for treatment after AMI. The first-stage technology, bare-metal stents (BMS), was associated with significant improvements in survival.[4] However, further development was suggested to overcome the disadvantages of BMS, resulting in the second-stage technology of drug-eluting stents (DES). In contrast to the conventional BMS, DES minimize the proliferation of cells within the vessel and prevent restenosis of the artery by eluting a drug, most often sirolimus or paclitaxel. Initial results suggested by Hiatt et al.[5] showed that DES seemed to be superior to BMS in the treatment of coronary artery disease.

So far, numerous economic evaluations have dealt with DES. However, results of existing studies are ambiguous. On the one hand, lower rates of restenosis have been reported for DES compared with BMS in most studies. On the other hand, there is evidence of an increased risk of thrombosis in patients treated with DES compared with BMS.[6] In addition, there are studies that suggest that higher initial costs of DES implantation due to higher prices for the device are partially compensated by a decrease in the costs for re-intervention.[7,8]

As most studies on DES are clinical trials, outcome measures might reflect efficacy rather than effectiveness. Economic evaluations based on these trials can likewise be suspected to reflect cost efficacy instead of the cost effectiveness of DES compared with BMS. Therefore, the objective of our study is to compare the costs and effectiveness of BMS versus DES in routine care in Germany. The use of administrative data enabled the analysis of large populations. As a consequence, the statistical power of our study is substantially higher than those of small clinical trials.

In contrast to analyses based on data from randomized controlled clinical trials (RCTs), the use of observational data may result in treatment selection bias as treatment assignment to DES or BMS implantation does not occur at random. Thus, patient cohorts might not be homogeneous in observable and unobservable characteristics. To preclude that differences in costs and effectiveness are a result of patient characteristics only, we implemented a propensity score matching (PSM)[9-13] in order to perform a retrospective quasi-randomization of patients. The PSM approach is based on the conditional independence assumption. …