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The simultaneous analysis of discrete and continuous outcomes in a dose-response study: using desirability functions
Todd Coffey1, Chris Gennings, Virginia C Moser
1Department of Biostatistics, Virginia Commonwealth University, PO Box 980032, Richmond, VA 23298, USA. jchen@nctr.fda.gov <jchen@nctr.fda.gov>
Regulatory Toxicology and Pharmacology : RTP
|March 3, 2007
Summary
This study introduces a new composite score using desirability functions to improve sensitivity in toxicology dose-response experiments. The method effectively detects low-level toxicity across multiple endpoints, enhancing risk assessment accuracy.
Area of Science:
- Toxicology
- Statistical Modeling
- Risk Assessment
Background:
- Toxicology dose-response experiments often measure multiple outcomes per animal.
- Analyzing individual endpoints can inflate the false-positive rate.
- A need exists for methods to combine diverse toxicological data effectively.
Purpose of the Study:
- To introduce a novel composite score method using desirability functions for toxicology dose-response analysis.
- To enhance the sensitivity of detecting toxicity, especially when effects are subtle or limited to a few endpoints.
- To provide a more robust statistical approach for evaluating chemical safety.
Main Methods:
- Developed a composite score by transforming discrete and continuous outcomes to a 0-to-1 scale using desirability functions.
- Combined transformed scores using the geometric mean.
- Fitted a nonlinear exponential model with a threshold parameter to the dose-response curve of the composite score.
Main Results:
- The composite desirability score demonstrated higher sensitivity to toxicity in a limited number of endpoints compared to sum-based composite scores.
- A statistically significant threshold parameter was identified, below the lowest tested dose.
- The method detected toxicity indicated by reduced cholinesterase levels, even when other endpoints remained unaffected.
Conclusions:
- The desirability function approach offers a sensitive method for analyzing toxicology dose-response data.
- This composite score effectively identifies low-level toxicity and improves the detection of adverse effects in toxicological studies.
- The method enhances the ability to assess chemical safety by integrating multiple outcome measures.
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