Rasch analysis of the intermittent and constant osteoarthritis pain (ICOAP) scale

Abstract

SummaryObjectivesThe Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire was developed to assess two forms of pain reported by people with osteoarthritis: intermittent and constant pain. Studies examining its measurement qualities have provided some support for its use as separate and total scales. However, it has not been previously evaluated using Rasch analysis. The current study examined the fit between data obtained from the ICOAP questionnaire and the Rasch model to determine whether it meets the requirements of interval-level measurement.DesignICOAP responses from 175 participants with knee osteoarthritis were collected in a cross-sectional questionnaire study. Participants were recruited from hospital clinics and a group who had taken part in previous research. The questionnaires were completed at home and returned by pre-paid envelope and the data were analysed using RUMM2020.ResultsFit to the Rasch model was achieved for both the Constant and Intermittent subscales following removal of a small number of items. The Total scale initially resulted in substantial misfit to the model, but fit was improved by removing four items that misfit the model. However, several participants presented with high fit residuals, which is consistent with misfit.ConclusionsThe results support the use of Constant and Intermittent subscales as unidimensional measures of pain. The Total scale can be adapted to improve fit to the Rasch model, but there are concerns over participant misfit.

Pain Phenotype in Patients With Knee Osteoarthritis: Classification and Measurement Properties of painDETECT and Self‐Report Leeds Assessment of Neuropathic Symptoms and Signs Scale in a Cross‐Sectional Study

“…Rasch‐converted scores were used in correlation analyses for both the questionnaire study and the PPT substudy, when available (for review, see ref. 14). Use of ICOAP subscale scores was supported by previous analyses 14.…”

“…14). Use of ICOAP subscale scores was supported by previous analyses 14. When appropriate, 95% confidence intervals (95% CIs) were calculated.…”

“…Questionnaires were checked for disordered response thresholds, differential item functioning (DIF) for sex and age (age <64 years, age 64–71 years, and age >71 years), response dependency, and unidimensionality (for review, see ref. 14). The person separation index (PSI) was reported for each scale.…”

Evaluation of a group acceptance commitment therapy intervention for people with knee or hip osteoarthritis: a pilot randomized controlled trial

“…As indicated by the Rasch analysis of the ICOAP [21], items 2, 8 and 11 were removed and as these items related to sleep and well-being; a separate ICOAP subscale was then created with these items. Rasch-analysis of the CPAQ [25] indicated that that the two CPAQ subscales, Activity Engagement (AE) and Pain Willingness (PW), should be analysed as separate scales.…”

“…Rasch analysis is a psychometric technique, which can be applied to both newly developed and existing questionnaires, enabling the advanced analysis of different measurement issues [21][22]. Data on an outcome measure are tested against the predictions of the Rasch model [24].…”