Categorizing a prognostic variable: Review of methods, code for easy implementation and applications to decision-making about cancer treatments Journal Article
| Authors: | Mazumdar, M.; Glassman, J. R. |
| Article 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 cutpoint 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. |
| Keywords: | treatment outcome; survival analysis; retrospective studies; cancer risk; antineoplastic agents; neoplasms; medical decision making; tomography, x-ray computed; cancer therapy; risk; statistical analysis; probability; models, statistical; lymphoma; testicular neoplasms; chi-square distribution; multivariate analysis; statistical model; biostatistics; seminoma; humans; prognosis; male; article |
| Journal Title: | Statistics in Medicine |
| Volume: | 19 |
| Issue: | 1 |
| ISSN: | 0277-6715 |
| Publisher: | John Wiley & Sons |
| Date Published: | 2000-01-15 |
| Start Page: | 113 |
| End Page: | 132 |
| Language: | English |
| DOI: | 10.1002/(sici)1097-0258(20000115)19:1<113::aid-sim245>3.0.co;2-o |
| PUBMED: | 10623917 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Export Date: 18 November 2015 -- Source: Scopus |
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