The ability to make good choices relies on the quality of information available and on the manner in which it is presented. The highest-quality information that can be presented to patients is that which is untinged from bias that distorts the comparative effectiveness of 1 treatment or approach over that of another. Two important bodies of literature consider instrumental variable (IV) methods to account for unmeasured confounding in observational data and the use of survival analysis methods to account for censoring of time-to-event outcomes. However, there is minimal research at the intersection of these areas. Especially lacking are IV methods for the Cox (proportional hazards) regression model.
