RT Journal
A1 Rassen JA, Schneeweiss S
T1 OUtcomes in the era of bare-metal stents vs the era of drug-eluting stents
JF JAMA
JO JAMA
YR 2009
FD January 7
VO 301
IS 1
SP 33
OP 34
DO 10.1001/jama.2008.899
UL http://dx.doi.org/10.1001/jama.2008.899
AB 
To the Editor: Dr Malenka and colleagues1 described the protective effect of drug-eluting stents against repeat revascularization procedures by comparing frequency of revascularization in the bare-metal stent era to the frequency after drug-eluting stents came on the market. In doing so, they took a step back from the exposure itself—drug-eluting vs bare-metal stent—and instead implicitly used the era as a proxy for the stent exposure. Presumably, they did this because they believed that the exposure to drug-eluting stent would be confounded by unmeasured factors that they could not adjust for with the available data.