Luke Keele
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View article: Covariate-assisted bounds on causal effects with instrumental variables
Covariate-assisted bounds on causal effects with instrumental variables Open
When an exposure of interest is confounded by unmeasured factors, an instrumental variable (IV) can be used to identify and estimate certain causal contrasts. Identification of the marginal average treatment effect (ATE) from IVs relies on…
View article: A primer on using balancing weights to estimate inverse probability weights
A primer on using balancing weights to estimate inverse probability weights Open
View article: Nonparametric Estimation of Local Treatment Effects with Continuous Instruments
Nonparametric Estimation of Local Treatment Effects with Continuous Instruments Open
Instrumental variable methods are widely used to address unmeasured confounding, yet much of the existing literature has focused on the binary instrument setting. Extensions to continuous instruments often impose strong parametric assumpti…
View article: So Many Choices: A Guide to Selecting Among Methods to Adjust for Observed Confounders
So Many Choices: A Guide to Selecting Among Methods to Adjust for Observed Confounders Open
Non‐randomised studies (NRS) typically assume that there are no differences in unobserved baseline characteristics between the treatment groups under comparison. Traditionally regression models have been deployed to estimate treatment effe…
View article: Local Effects of Continuous Instruments without Positivity
Local Effects of Continuous Instruments without Positivity Open
Instrumental variables are a popular study design for the estimation of treatment effects in the presence of unobserved confounders. In the canonical instrumental variables design, the instrument is a binary variable. In many settings, how…
View article: Minimally invasive colorectal cancer surgery: an observational study of medicare advantage and fee-for-service beneficiaries
Minimally invasive colorectal cancer surgery: an observational study of medicare advantage and fee-for-service beneficiaries Open
View article: Longitudinal Increases in Time to Surgery for Patients with Breast Cancer: A National Cohort Study
Longitudinal Increases in Time to Surgery for Patients with Breast Cancer: A National Cohort Study Open
Background Longer time to surgery (TTS) is associated with worse survival in patients with breast cancer. Whether this association has encouraged more prompt care delivery remains unknown. Methods The National Cancer Database was used to i…
View article: Review 1: "Parallel Trends in an Unparalleled Pandemic: Difference-in-Differences for Infectious Disease Policy Evaluation"
Review 1: "Parallel Trends in an Unparalleled Pandemic: Difference-in-Differences for Infectious Disease Policy Evaluation" Open
Reviewers commend the study for addressing the limitations of standard DiD methods and proposing robust alternatives. They suggest further elaboration on the differences between the new methods and traditional estimates, as well as compari…
View article: Reviews of "Parallel Trends in an Unparalleled Pandemic: Difference-in-Differences for Infectious Disease Policy Evaluation"
Reviews of "Parallel Trends in an Unparalleled Pandemic: Difference-in-Differences for Infectious Disease Policy Evaluation" Open
View article: Approximate balancing weights for clustered observational study designs
Approximate balancing weights for clustered observational study designs Open
In a clustered observational study, a treatment is assigned to groups and all units within the group are exposed to the treatment. We develop a new method for statistical adjustment in clustered observational studies using approximate bala…
View article: Identifying High and Low Performing Emergency General Surgery Hospitals Using Direct Standardization
Identifying High and Low Performing Emergency General Surgery Hospitals Using Direct Standardization Open
Importance Variation in outcomes for emergency general surgery conditions has been shown at the hospital level. Few have examined difference across hospitals for older adults who often present with the greatest risk. To date, no one has ex…
View article: Nonparametric identification and efficient estimation of causal effects with instrumental variables
Nonparametric identification and efficient estimation of causal effects with instrumental variables Open
Instrumental variables are widely used in econometrics and epidemiology for identifying and estimating causal effects when an exposure of interest is confounded by unmeasured factors. Despite this popularity, the assumptions invoked to jus…
View article: Flexibly Estimating and Interpreting Heterogeneous Treatment Effects of Laparoscopic Surgery for Cholecystitis Patients
Flexibly Estimating and Interpreting Heterogeneous Treatment Effects of Laparoscopic Surgery for Cholecystitis Patients Open
Laparoscopic surgery has been shown through a number of randomized trials to be an effective form of treatment for cholecystitis. Given this evidence, one natural question for clinical practice is: does the effectiveness of laparoscopic su…
View article: Costs of Care for Operative and Nonoperative Management of Emergency General Surgery Conditions
Costs of Care for Operative and Nonoperative Management of Emergency General Surgery Conditions Open
Objective: Many emergency general surgery (EGS) conditions can be managed operatively or nonoperatively, with outcomes that vary by diagnosis. We hypothesized that operative management would lead to higher in-hospital costs but to cost sav…
View article: Primary Care Physician Follow-Up and 30-Day Readmission After Emergency General Surgery Admissions
Primary Care Physician Follow-Up and 30-Day Readmission After Emergency General Surgery Admissions Open
Importance The benefit of primary care physician (PCP) follow-up as a potential means to reduce readmissions in hospitalized patients has been found in other medical conditions and among patients receiving high-risk surgery. However, littl…
View article: An acute care surgeon's dilemma: Operative vs. non-operative management of emergency general surgery conditions in patients with recent colorectal cancer treatment
An acute care surgeon's dilemma: Operative vs. non-operative management of emergency general surgery conditions in patients with recent colorectal cancer treatment Open
View article: Delayed time to radiation and overall survival in Merkel cell carcinoma
Delayed time to radiation and overall survival in Merkel cell carcinoma Open
Background Clinically localized Merkel cell carcinoma (MCC) is commonly treated with surgical excision and radiotherapy. The relationship between time to adjuvant radiotherapy and overall survival (OS) remains understudied. Methods This re…
View article: Emergency Surgery, Multimorbidity and Hospital-Free Days: A Retrospective Observational Study
Emergency Surgery, Multimorbidity and Hospital-Free Days: A Retrospective Observational Study Open
View article: Conditional Effects of Race on Operative and Nonoperative Outcomes of Emergency General Surgery Conditions
Conditional Effects of Race on Operative and Nonoperative Outcomes of Emergency General Surgery Conditions Open
Introduction: Many emergency general surgery (EGS) conditions can be managed both operatively or nonoperatively; however, it is unknown whether the decision to operate affects Black and White patients differentially. Methods: We identified…
View article: Association of Established Primary Care Use With Postoperative Mortality Following Emergency General Surgery Procedures
Association of Established Primary Care Use With Postoperative Mortality Following Emergency General Surgery Procedures Open
Importance Sixty-five million individuals in the US live in primary care shortage areas with nearly one-third of Medicare patients in need of a primary care health care professional. Periodic health examinations and preventive care visits …
View article: Doubly robust machine learning for an instrumental variable study of surgical care for cholecystitis
Doubly robust machine learning for an instrumental variable study of surgical care for cholecystitis Open
Comparative effectiveness research frequently employs the instrumental variable design since randomized trials can be infeasible for many reasons. In this study, we investigate and compare treatments for emergency cholecystitis -- inflamma…
View article: Minimax optimal subgroup identification
Minimax optimal subgroup identification Open
Quantifying treatment effect heterogeneity is a crucial task in many areas of causal inference, e.g. optimal treatment allocation and estimation of subgroup effects. We study the problem of estimating the level sets of the conditional aver…
View article: National Cohort Study of Resource Utilization in Older Adults With Emergency General Surgery Conditions
National Cohort Study of Resource Utilization in Older Adults With Emergency General Surgery Conditions Open
View article: The Conditional Effects of Multimorbidity on Operative Versus Nonoperative Management of Emergency General Surgery Conditions
The Conditional Effects of Multimorbidity on Operative Versus Nonoperative Management of Emergency General Surgery Conditions Open
Objective: To understand how multimorbidity impacts operative versus nonoperative management of emergency general surgery (EGS) conditions. Background: EGS is a heterogenous field, encompassing operative and nonoperative treatment options.…
View article: Improving instrumental variable estimators with post-stratification
Improving instrumental variable estimators with post-stratification Open
Experiments studying get-out-the-vote (GOTV) efforts estimate the causal effect of various mobilization efforts on voter turnout. However, there is often substantial noncompliance in these studies. A usual approach is to use an instrumenta…
View article: Covariate Adjustment in Regression Discontinuity Designs
Covariate Adjustment in Regression Discontinuity Designs Open
This chapter reviews the different roles of covariate adjustment in the regression discontinuity (RD) literature, and to offer methodological guidance for its correct use in applications. One of the most important roles of baseline covaria…
View article: Comparison of Simulated Outcomes of Colorectal Cancer Surgery at the Highest-Performing vs Chosen Local Hospitals
Comparison of Simulated Outcomes of Colorectal Cancer Surgery at the Highest-Performing vs Chosen Local Hospitals Open
Importance Variation in outcomes across hospitals adversely affects surgical patients. The use of high-quality hospitals varies by population, which may contribute to surgical disparities. Objective To simulate the implications of data-dri…
View article: A Guide to Regression Discontinuity Designs in Medical Applications
A Guide to Regression Discontinuity Designs in Medical Applications Open
We present a practical guide for the analysis of regression discontinuity (RD) designs in biomedical contexts. We begin by introducing key concepts, assumptions, and estimands within both the continuity-based framework and the local random…
View article: Covariate-assisted bounds on causal effects with instrumental variables
Covariate-assisted bounds on causal effects with instrumental variables Open
When an exposure of interest is confounded by unmeasured factors, an instrumental variable (IV) can be used to identify and estimate certain causal contrasts. Identification of the marginal average treatment effect (ATE) from IVs relies on…
View article: Approximate Balancing Weights for Clustered Observational Study Designs
Approximate Balancing Weights for Clustered Observational Study Designs Open
In a clustered observational study, a treatment is assigned to groups and all units within the group are exposed to the treatment. We develop a new method for statistical adjustment in clustered observational studies using approximate bala…