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.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04072005-123926 |
| Date | 14 June 2005 |
| Creators | O'Day, Terrence |
| Contributors | John Kellum, Lan Kong, Lisa Weissfeld, Derek Angus |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04072005-123926/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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