CatReg Software for Categorical Regression Analysis (May 2016)
Since its introduction by EPA in 2006, CatReg was available only as an application written in and run using the R statistics package. The new CatReg Version 3.0 requires R be installed and relies on the same statistical algorithms, but offers a Windows-based interface that makes specifying variables, filters, stratification, clustering, hypotheses, and applying the algorithms an easier and more efficient experience.
CatReg was developed to support risk assessors, toxicologists, and health scientists in conducting exposure-response analyses, most often for controlled animal experiments. CatReg reads data from ordinary comma-separated data files and outputs both plots and text-based results.
CatReg can be used to perform categorical regression analyses on toxicity data after effects have been assigned to ordinal severity categories (e.g., no effect, adverse effect, severe effect) and associated with up to two independent variables corresponding to the exposure conditions (e.g., concentration and duration) under which the effects occurred. CatReg calculates the probabilities of the different severity categories over the continuum of the variables describing exposure conditions. The categorization of observed responses allows expression of dichotomous, continuous, and descriptive data in terms of effect severity and supports the analysis of data from single studies or a combination of similar studies.
There are many potential applications of the CatReg program in the analysis of health effects studies and other types of data. It was originally developed to support toxicity assessments for acute inhalation exposures, but modifications have been made to the software (e.g., the ability to estimate background responses and derive upper and lower bound confidence limits on BMD estimates) that facilitate its broader use for the evaluation of chronic studies and for its use in the derivation of traditional EPA Integrated Risk Information System (IRIS) reference values.
Special Features
- Stratifying the analysis by user-specified covariates (e.g., species, sex, etc.)
- Choosing among several basic forms of the exposure-response curve
- Using effects assigned to a range of severity categories, rather than a single category
- Using cluster-correlated data
- Using aggregate data
- Filtering data to analyze subsets of data and perform sensitivity analyses
- User-friendly hypothesis testing interface that can be used to determine whether data associated with variables such as gender, species, genetics, and other factors that can influence a dose-response-time relationship should be pooled together or analyzed separately for estimating the model parameters (e.g., intercept, dose, and time model coefficients)
CatReg reads data from comma-separated values (CSV) formatted text files.
For screenshots and more information on CatReg, download and view the CatReg User Guide.
CatReg 3.0 Requires R
All versions of CatReg rely on the open source package R EXIT to perform all statistical calculations. To use CatReg, you must have version 3.1 or later of the R statistical software installed on your computer.
R-only CatReg Version
CatReg 2.3, the R-only version of the software released in August 2012, is still available for download. The download file includes sample data files and a PDF user guide. You must download and install the latest version of R to run this CatReg version.
Note: None of the statistics in 2.3 have changed in CatReg 3.0, except that the Windows version provides automatic hypothesis testing.
Impact/Purpose
The software was developed to support toxicity assessment for acute inhalation exposures, but the U.S. Environmental Protection Agency (EPA) encourages the broad application of this software.History/Chronology
| Date | Description |
|---|---|
| 01- Feb 2000 | EPA developed CatReg documentation and software (S-PLUS® version) |
| 02- Apr 2000 | EPA published CatReg user manual (S-PLUS® version). |
| 03- Aug 2006 | EPA released version 2.0 (R-version) of the Catreg Software for Categorical Regression Analysis tool. |
| 04- Nov 2006 | EPA released the draft, CatReg Software User Manual (R-version) (U.S. EPA, 2006) (94 pp, 925 KB, about PDF). |
| 05- Dec 2006 | EPA added the CSV Sample files (Zip). |
| 06- Apr 2007 | EPA posted the CatReg Training Slides (114 pp, 752 KB, about PDF). |
| 07- Feb 2011 | EPA released CatReg version 2.1. |
| 08- Jul 2012 | EPA released CatReg version 2.2. |
| 09- Aug 2012 | EPA released CatReg version 2.3. |
| 10- May 2016 | EPA released CatReg version 3.0. |
Download(s)
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.