DOI: 10.3886/icpsr39631
title: Advancing Patient Centered Outcomes Research in Survival Data with Unmeasured Confounding to Improve Patient Risk Communication [Methods Study], United States and Canada, 2015-2019
title: Archival Version

description: Researchers often use data from patients' health records to compare treatments. But many things--not just treatments--affect patients' health. To figure out whether changes in patients' health result from treatment or something else, researchers can use statistical methods called instrumental variables, or IVs. IV methods account for factors that affect health but aren't in patients' health records, such as eating habits. Existing IV methods work well when looking at health outcomes that are measured using certain types of scales, such as blood pressure. But existing methods don't work as well to measure the time until a health event occurs, particularly when an event, like death, has not occurred for many patients in the study.
In this study, the research team created and tested a new IV method to more accurately estimate how a treatment relates to the time until a health event.
description: To develop, test, and apply IV methods for survival analysis using the Cox proportional hazard model
description: Researchers developed the two-stage residual inclusion-frailty (2SRI-F) method to estimate hazard ratios from Cox models. To address unmeasured confounders, 2SRI-F emulates the two-stage residual inclusion (2SRI) procedure by using the residuals, or the differences, between the actual treatment status and the predicted probability of receiving the treatment in addition to the IVs as predictors for estimating treatment effects. However, 2SRI-F also accounts for the fact that the residuals are imperfect surrogates for unmeasured confounders; which in turn better enables the substituted residuals to account for unmeasured confounding effects. To evaluate the performance of these IV methods, researchers conducted Monte Carlo simulations testing different scenarios.
Using patient data from the Vascular Quality Initiative (VQI) registry, researchers conducted three studies to test the performance of 2SRI-F. In study 1, researchers linked Medicare claims data to VQI registry data from patients who underwent carotid endarterectomy or carotid stenting between 2003 and 2016. They compared mortality hazard ratios estimated from the 2SRI-F method with those from existing methods. Study 2 examined the effect of intervention type on time to death from any cause in patients with an abdominal aortic aneurysm. Study 3 estimated the impact of endovascular atherectomy versus traditional peripheral vascular interventions on the time to any type of amputation or any type of reintervention.
A nine-member panel including patients, physicians, and the VQI director provided input and helped design the research plan.
description: Datasets: 
DS1: Advancing Patient Centered Outcomes Research in Survival Data with Unmeasured Confounding to Improve Patient Risk Communication [Methods Study], United States and Canada, 2015-2019
description: Patients with vascular disease who are treated by physicians and hospitals that participate in the Vascular Quality Initiative (VQI)..