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EmilyRoberts20211215
(08 Dec 2021,
SimonVandekar
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-- Main.RameelaChandrasekhar - 29 Nov 2021 %HEAD{ NAME="Emily Roberts, !PhD Candidate" AFFILIATION="Department of Biostatistics, University of Michigan, MI" TITLE="Surrogacy Validation with Longitudinal Outcomes for a Gene Therapy" IMAGELINK="https://sph.umich.edu/biostat/phd-student-profiles/images/roberts%20emily.JPG" }% Valid surrogate endpoints can be used as a substitute for a true outcome of interest to measure treatment efficacy in a clinical trial. Our work is motivated by a trial of a gene therapy where the functional outcomes are measured repeatedly. We propose a causal inference approach to validate a surrogate by incorporating baseline covariates and longitudinal measurements using a mixed modeling approach, and we define models and quantities for validation that may vary across the study period using principal surrogacy criteria. We consider a surrogate-dependent treatment efficacy curve that allows us to validate the surrogate at different time points, or integrate over multiple time points for an overall measure of surrogate validity. We extend these methods to accommodate a crossover design where all patients eventually receive the treatment. Because not all parameters are statistically identified in the general setting, we rely on informative prior distributions to obtain inference. We consider the sensitivity of these prior assumptions as well as assumptions of independence among certain counterfactual quantities conditional on pre-treatment covariates to improve identifiability. %TAIL{DATE="15 December 2021"}% <!-- * Set HEAD = <div class="w3-card-2" id="task" style="max-width:750px; margin-left: 0px;"> <header class="w3-container w3-blue" style="padding:40px"><h1>Biostatistics Weekly Seminar</h1><br><h2 style="color:white;">%TITLE%<br><br>%NAME%<br>%AFFILIATION%</h2></header><div class="w3-container" style="padding:40px"><IMG SRC=%IMAGELINK% align="left" id="mug"/> * Set TAIL = <br><h3>Hybrid format: MRB 3, Room 1220 (Zoom link to follow)<br>%DATE%<br>1:30pm</h3></div></div><br>[[%TOPIC%Itinerary][Speaker Itinerary]] --> <style> .w3-card-2,.w3-example{box-shadow:0 2px 4px 0 rgba(0,0,0,0.16),0 2px 10px 0 rgba(0,0,0,0.12)!important} .w3-blue,.w3-hover-blue:hover{color:#fff!important;background-color:#2196F3!important} .w3-container{padding:0.01em 16px} .foswikiTopic {font-family: 'Open Sans', sans-serif;} /* Removes location hierarchy (usually written in grey text) */ .patternHomePath {display:none;} /* Removes bar with edit and attach buttons and location hierarchy */ .patternTop{display:none;} h1, h2, h3, h4, h5, h6{font-family: 'Montserrat','Open Sans', sans-serif;font-weight:700;} h1, h2, h3, h4, h5, h6{color:#bf1735;} h1:first-of-type{color:#2a3e6e;margin-bottom:25px;margin-top:5px;} .foswikiImage{margin-left:-9px;} img#mug{padding-right: 40px; padding-bottom:25px; height:250px;} </style>
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Topic revision: r3 - 08 Dec 2021,
SimonVandekar
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