Comparison of Warfarin and Aspirin in Preventing Symptoms Causedby Atherosclerotic Intracranial Arterial Stenosis by UsingPrincipal Stratification Pubblico

Abstract

Abstract

Comparison of Warfarin and Aspirin in Preventing Symptoms Caused by Atherosclerotic Intracranial Arterial Stenosis by Using Principal Stratification

Yaping Wang

When estimating causal effects, most currently available methods focus on adjusting pre-treatment variables, while ignoring the post-treatment variables. However, the post-treatment variables are also important in sample classification and need to be considered in causal effect estimation. Recently, the principal stratification strategy provides a way to take account of post-treatment variables in causal inference. The object of this study is to compare the efficiency and safety of aspirin and warfarin in preventing the risk of stroke by using principal stratification strategy. The dataset used in our study came from Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) study, where 569 patients were enrolled. The dose of warfarin was controlled by making the target International Normalized Ratio (INR) in the range from 2 to 3, and the dose of aspirin was 1300 mg/day. The INR score was treated as a post- treatment variable, which was potentially influenced by the use of warfarin. Based on the principal stratification models, the estimated Odds Ratio of primary end point for warfarin versus aspirin treatment is 0.78 [95% CI (0.38, 1.60)], which is attributable to the INR ranges. From the results obtained by applying principal stratification, we conclude that warfarin and aspirin are not significantly different in preventing the outbreak ischemic stroke, brain hemorrhage, or death from vascular causes other than stroke. Moreover, warfarin is found to be associated with significantly higher rates of death and major hemorrhage[1]. Hence, the common practice of administering warfarin rather than aspirin for symptomatic intracranial arterial stenosis is not supported.

Table of Contents

Table of Contents

Chapter 1 - Introduction 1.1 Stroke 1.2 WASID Study Design 1.3 WASID Study Results 1.4 Question Chapter 2 - Method 2.1 Causal Analysis 2.2 Principal Stratification 2.3 Brief Review of Principal Effect in Needle Exchange Program Chapter 3 - Construct Principal Stratification 3.1 WASID dataset 3.2 Models used in Principal Stratification Chapter 4 - Result Chapter 5 - Discussion 5.1 Result compared to WASID study 5.2 Implication for Practice 5.3 Limitation of findings 5.4 Recommendations Tables Appendix: SAS and R code SAS Code: R code: Clinical Coordinating Center (CCC)

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About this Dissertation

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School	Laney Graduate School
Department	Biostatistics
Degree	MS
Submission	Dissertation
Language	English
Research Field	Biology, Biostatistics Statistics
Parola chiave	Warfarin Causal Analysis Aspirin Principal Stratification Stroke Atherosclerotic Intracranial Arterial Stenosis
Committee Chair / Thesis Advisor	Hertzberg, Vicki S, Emory University
Committee Members	Cotsonis, George A, Emory University

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