Categorizing a prognostic variable: Review of methods, code for easy implementation and applications to decision-making about cancer treatments Book Section
| Authors: | Mazumdar, M.; Glassman, J. R. |
| Editor: | D'Agostino, R. B. |
| Article/Chapter Title: | Categorizing a prognostic variable: Review of methods, code for easy implementation and applications to decision-making about cancer treatments |
| Abstract: | Categorizing prognostic variables is essential for their use in clinical decision-making. Often a single outpoint that stratifies patients into high-risk and low-risk categories is sought. These categories may be used for making treatment recommendations, determining study eligibility, or to control for varying patient prognoses in the design of a clinical trial. Methods used to categorize variables include: biological determination (most desirable but often unavailable); arbitrary selection of a cutpoint at the median value; graphical examination of the data for a threshold effect; and exploration of all observed values for the one which best separates the risk groups according to a chi-squared test. The last method, called the minimum p-value approach, involves multiple testing which inflates the type I error rates. Several methods for adjusting the inflated p-values have been proposed but remain infrequently used. Exploratory methods for categorization and the minimum p-value approach with its various p-value corrections are reviewed, and code for their easy implementation is provided. The combined use of these methods is recommended, and demonstrated in the context of two cancer-related examples which highlight a variety of the issues involved in the categorization of prognostic variables. Copyright © 2004 John Wiley & Sons Ltd. All Rights Reserved. |
| Book Title: | Tutorials in Biostatistics: Statistical Methods in Clinical Studies |
| Volume: | 1 |
| ISBN: | 978-0-470-02365-5 |
| Publisher: | Wiley Blackwell |
| Publication Place: | West Sussex, UK |
| Date Published: | 2004-01-01 |
| Start Page: | 187 |
| End Page: | 208 |
| Language: | English |
| DOI: | 10.1002/0470023678.ch2a |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Book Chapter: 2.1 -- Tutorials in Biostat., Stat. Methods in Clin. Stud. -- 9780470023679 (eISBN); 0470023651 (ISBN); 9780470023655 (ISBN) -- Export Date: 3 February 2016 -- Source: Scopus |
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