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TOBIT REGRESSION AND CENSORED CYTOKINE DATA

O'Day, Terrence (2005) TOBIT REGRESSION AND CENSORED CYTOKINE DATA. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Well designed clinical studies theoretically produce accurate data from which a reasonable conclusion(s) may be drawn. Data accuracy may be hindered by the measurement tool or device. Additionally, the data may be in such a form that it is problematic from an analytic and interpretive point of view. An example of such a problematic form may be seen in censored, sample-selected, or truncated data. Clinical data may be particularly prone to censoring or truncation since various assays used to measure patient parameters have limited sensitivity. Lower and upper limits of assay sensitivity may have a direct impact on the clinical diagnosis and prognosis of the patient, especially if the patient is a high risk critical care patient. The aim of this report is to estimate mean cytokine levels using various approaches, including the arithmetic and geometric mean, and mean estimation from a tobit model. The data set is from the Department of Critical Care Medicine and contains values for several cytokines from 1753 patients (discharge status) or 1610 patients (follow-up status), including Interleukin 6 (IL-6), Interleukin 10 (IL-10), and Tumor Necrosis Factor (TNF). A brief overview of the immune system and its relationship to cytokine production will be presented prior to an explanation of the estimation procedures. Finally, recommendations for estimating a mean from the censored data set will be presented. Although not specific to Critical Care Medicine, the problem of censored data is evident in many areas of study, specifically Public Health. Guidelines for dealing with censored data would be a significant and valuable tool for Public Health professionals.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
O'Day, Terrencemarshallgh@adelphia.net
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWeissfeld, Lisalweis@pitt.eduLWEIS
Committee MemberAngus, Derekangusdc@ccm.upmc.edu
Committee MemberKellum, Johnkellumja@ccm.upmc.eduKELLUM
Committee MemberKong, Lanlkong@pitt.eduLKONG
Date: 14 June 2005
Date Type: Completion
Defense Date: 6 April 2005
Approval Date: 14 June 2005
Submission Date: 7 April 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Graduate School of Public Health > Biostatistics
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: censored; tobit; truncated
Other ID: http://etd.library.pitt.edu/ETD/available/etd-04072005-123926/, etd-04072005-123926
Date Deposited: 10 Nov 2011 19:34
Last Modified: 19 Dec 2016 14:35
URI: http://d-scholarship.pitt.edu/id/eprint/6843

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