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Rasch analysis of the intermittent and constant osteoarthritis pain (ICOAP) scale
B J Moreton1, M Wheeler, D A Walsh
1Arthritis Research U.K. Pain Centre, University of Nottingham, UK. bryan.moreton@nottingham.ac.uk
Osteoarthritis and Cartilage
|July 10, 2012
Summary
The intermittent and constant osteoarthritis pain (ICOAP) questionnaire shows promise for measuring osteoarthritis pain. Rasch analysis indicates its subscales are suitable for interval-level measurement, though the total scale needs refinement.
Area of Science:
- Rheumatology
- Psychometrics
- Health Measurement
Background:
- Osteoarthritis pain is complex, with intermittent and constant pain types.
- The Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire assesses these pain types.
- Previous studies support the ICOAP's measurement qualities, but Rasch analysis was lacking.
Purpose of the Study:
- To evaluate the ICOAP questionnaire using Rasch analysis.
- To determine if the ICOAP meets requirements for interval-level measurement of osteoarthritis pain.
Main Methods:
- Cross-sectional study of 175 knee osteoarthritis patients.
- Data collected via questionnaires completed at home.
- Analysis performed using RUMM2020 software.
Main Results:
- The Constant and Intermittent subscales demonstrated good fit to the Rasch model after item refinement.
- The Total scale initially showed misfit but improved after removing four misfitting items.
- Some participants exhibited high fit residuals, indicating potential individual misfit.
Conclusions:
- The Constant and Intermittent subscales are supported as unidimensional measures of osteoarthritis pain.
- The ICOAP Total scale can be adapted for better Rasch model fit.
- Concerns regarding participant misfit warrant further investigation.
