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JonathanSchildcrout20210203
(21 Jan 2021,
AndrewSpieker
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%HEAD{ NAME="Jonathan Schildcrout, !PhD" AFFILIATION="Vanderbilt University Medical Center" TITLE="Direct marginal model analyses of longitudinal, ordinal outcomes with absorbing states" IMAGELINK="https://www.vumc.org/biostatistics/sites/default/files/people/Jonathan%20Schildcrout.jpg" }% Studies of critically ill, hospitalized patients often follow participants over a fixed follow-up period and characterize daily patient health with an ordinal scale. While, at first glance, longitudinal proportional odds models appear to be a natural choice in these setting, a challenge arises when one or more of the outcome states is absorbing (i.e., no one exits from the state once they enter it). In these settings, the proportional odds assumption for outcome associations with follow-up day are likely to be violated, and so partial proportional odds models may be required to ensure valid inferences. Motivated by the Violet 2 Study, a randomized clinical trial of Vitamin D on critically ill patients, we describe modeling approaches that capture intervention effects over time with a four-level ordinal outcome (not alive, on mechanical ventilator or with acute respiratory distress syndrome, in hospital, at home) where the lowest (not alive) state is absorbing and the highest (at home) state is nearly absorbing. For this purpose, we will discuss extensions of the proportional odds model for longitudinal data. We will focus on direct estimation of marginal mean model parameters using likelihood-based analysis procedures that can naturally handle absorbing states. We illustrate the utility of the modeling procedure through simulation studies and analysis of the Violet 2 study data. %TAIL{DATE="03 February 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>Zoom (Link to Follow)<br>%DATE%<br>1:30pm</h3></div></div><br> --> <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: r1 - 21 Jan 2021,
AndrewSpieker
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