Reply: Bleeding after PCI, vascular access, and falsification endpoints in observational studies

摘要

We appreciate the interest and perspective of Dr. Valencia-Serrano and colleagues on our exploration of the use of falsification end-points as a method of exploring the potential for residual confounding in observational comparative effectiveness studies (1). We believe that such endpoints, akin to negative controls in experimental methods, are an underutilized tool in the cardiovascular data. We have used the examination of nonaccess site bleeding in comparing transradial and transfemoral access in percutaneous coronary intervention (PCI) as a simple illustrative example of how such a method might be used in practice. The utility of any falsification endpoint rests on the assumption that the treatments being compared should not differ with respect to their influence on these endpoints. In this case, the assumption is that the route of access for PCI, whether trans-radial or transfemoral, should not influence the rate of nonaccess site bleeding in a causal manner. Dr. Valencia-Serrano and colleagues propose that the differences observed in the falsification endpoint in our analysis may, in fact, be due to a causal relationship between the site of arterial access and nonaccess site bleeding, mediated through the "hemorrhagic transformation of clinically unapparent embolic infarctions" related to catheter contact with the aorta during transfemoral procedures.