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More relevant, precise, and efficient items for assessment of physical function and disability: moving beyond the
J F Fries1, B Bruce, J Bjorner
1Stanford University, 1000 Welch Road, Suite 203, Palo Alto, CA 94304, USA. jff@stanford.edu.
Annals of the Rheumatic Diseases
|October 14, 2006
Summary
Improving patient-reported outcome (PRO) items enhances measurement precision and clarity. This study refined physical function/disability items, leading to better instrument performance and potentially smaller clinical trial sample sizes.
Area of Science:
- Health Measurement
- Clinical Epidemiology
- Psychometrics
Background:
- Patient-reported outcomes (PROs) are crucial study endpoints.
- Item performance in PRO instruments requires optimization for precision and clarity.
- Physical function/disability items are key components of many PRO instruments.
Purpose of the Study:
- To improve the performance of physical function/disability items within PRO instruments.
- To enhance the clarity, relevance, and information content of measurement items.
- To reduce sample size requirements in clinical trials through improved item design.
Main Methods:
- Analysis of 1860 physical function/disability items from 165 instruments.
- Utilized modified Delphi consensus, respondent feedback, and item response theory (IRT).
- Data collected from 1100 subjects with arthritis, osteoarthritis, and normal aging.
Main Results:
- Present tense items were clearer, better understood, and more translatable than past tense items.
- Brief, clear items measuring a single construct with 4-5 response options were optimal.
- IRT identified four subdomains of disability: mobility, dexterity, axial, and compound.
Conclusions:
- Significant improvements in PRO item and instrument performance are achievable.
- Optimized items enhance measurement precision and reduce potential bias.
- Enhanced PRO instruments can lead to substantial reductions in clinical trial sample sizes.
