Evaluating the effectiveness of a rapidly adopted cardiovascular technology with administrative data: The case of drug-eluting stents for acute coronary syndromes

Abstract

Background Instrumental variable (IV) methods can correct for unmeasured confounding when using administrative (claims) data for cardiovascular outcomes research, but difficulties identifying valid IVs have limited their use. We evaluated the safety and efficacy of drug-eluting coronary stents (DES) compared to bare metal stents (BMS) for Medicare beneficiaries with acute coronary syndromes (ACS) using the rapid uptake of DES in clinical practice as an instrument. We compared results from IV to those from propensity score matching (PSM) and multivariable regression models. Methods Retrospective cohort study involving 62,309 fee-for-service beneficiaries aged 66 and older treated with coronary stenting between May 2003 and February 2004. Outcomes were measured for 46 months after revascularization using claims data. Results DES recipients were younger, had lower prevalence of myocardial infarction, and had fewer comorbidities compared to BMS recipients. Use of DES was associated with lower rates of mortality by PSM (HR 0.80, CI: [0.77, 0.83]) but not by IV (HR 0.99, CI: [0.87, 1.11]). IV models estimated a larger reduction in repeat revascularization (HR 0.76, CI: [0.63, 0.89]) than did PSM (HR 0.90, CI: [0.87, 0.93]). Conclusions Based on IV analysis, the increased utilization of DES relative to BMS among Medicare beneficiaries with ACS is associated with reduced rates of repeat revascularization and no difference in mortality. IV approaches provide a useful complement to conventional approaches to cardiovascular outcomes research with administrative data.

External Adjustment Sensitivity Analysis for Unmeasured Confounding: An Application to Coronary Stent Outcomes, Pennsylvania 2004–2008

“…However, we note that hospital DES adoption dates had also been conjectured as possibly correlated with contemporaneous rates of DES use (Malenka, Skinner, and Lucas ), and similar time‐based instruments have been used more recently (Federspiel et al. ; Venkitachalam et al. ).…”

“…Other recent studies find no benefit for DES using DES adoption time as an IV for stent type (Federspiel et al. ; Venkitachalam et al. ).…”

“…Recent studies controlling for such biases using instrumental variable (IV) approaches have unexpectedly found no mortality benefit for DES (Federspiel et al. ; Venkitachalam et al. ).…”

“…Given the widespread use of DES in the community, understanding the robustness of existing real-world studies to such potential biases is important. Recent studies controlling for such biases using instrumental variable (IV) approaches have unexpectedly found no mortality benefit for DES (Federspiel et al 2012;Venkitachalam et al 2011). However, IV studies are sensitive to choice of instrument, can have low power, may mask treatment heterogeneity, and inference beyond the marginal patients on which the IVestimates are identified can be limited (McClellan, McNeil, and Newhouse 1994;Harris and Remler 1998;Basu et al 2007).…”

Instrumental Variable Analysis to Compare Effectiveness of Stents in the Extremely Elderly

“…In the case of the introduction of new medical technology, variation in use rates with time is one such natural experiment that can be used to examine the comparative effectiveness of alternative therapies and devices. [6][7][8] (BMS) resulted in pronounced uncertainty about the balance of ischemic and bleeding risk for elderly patients, a growing population of PCI patients who are subject to higher risks of each of these types of clinical outcomes as well as mortality. 10,11 We examined the use of DES with time in patients ≥85 years of age within a mandatory state procedure database.…”