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Comparing broad and narrow phenotype algorithms: differences in performance characteristics and immortal time
Joel N Swerdel1,2, Mitchell M Conover1,2
1Observational Health Data Analytics, Global Epidemiology, Janssen Research and Development, Titusville, NJ, United States.
Summary
Adding a second diagnosis code to phenotype algorithms increases specificity but also incurs immortal time. This trade-off is crucial for accurate observational research using electronic health records.
Area of Science:
- Observational health research
- Health informatics
- Biostatistics
Background:
- Developing accurate phenotype algorithms for observational research often involves a trade-off between sensitivity and specificity.
- Existing algorithms may not adequately balance these performance characteristics, potentially impacting study validity.
Purpose of the Study:
- To evaluate the performance characteristics of phenotype algorithms designed to enhance specificity.
- To quantify the amount of immortal time associated with these specificity-enhanced algorithms.
Main Methods:
- Examined algorithms for 11 chronic health conditions across five databases.
- Developed five algorithms per condition: one broad (single code) and four narrow (requiring a second code within varying time windows).
- Assessed sensitivity, positive predictive value (PPV), and the proportion of immortal time relative to time-at-risk (TAR).
Main Results:
- Narrow algorithms demonstrated higher PPV and lower sensitivity compared to the single-code algorithm.
- Increasing the time window for the second diagnosis code improved algorithm sensitivity.
- A larger window for the second diagnosis code increased immortal time, with the highest proportion observed in shorter TAR analyses.
Conclusions:
- Using a second diagnosis code can effectively increase the specificity of health condition algorithms.
- This approach introduces immortal time, representing a significant trade-off that must be considered in study design.
- Careful consideration of algorithm design is necessary to balance specificity and minimize immortal time in observational research.
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