Comparison of measurement properties of the P4 pain scale and disease specific pain measures in patients with knee osteoarthritis

S M Robbins; R Rastogi; J Howard; R Rosedale

doi:10.1016/j.joca.2014.03.018

Comparison of measurement properties of the P4 pain scale and disease specific pain measures in patients with knee osteoarthritis

Osteoarthritis Cartilage. 2014 Jun;22(6):805-12. doi: 10.1016/j.joca.2014.03.018. Epub 2014 Apr 8.

Authors

S M Robbins¹, R Rastogi², J Howard³, R Rosedale⁴

Affiliations

¹ Centre for Interdisciplinary Research in Rehabilitation, Constance Lethbridge Rehabilitation Centre, and School of Physical and Occupational Therapy, McGill University, Montreal, Canada. Electronic address: shawn.robbins@mcgill.ca.
² Department of Physiotherapy, London Health Sciences Centre, London, Canada. Electronic address: ravi.rastogi@lhsc.on.ca.
³ Division of Orthopedic Surgery, Western University and London Health Sciences Centre, London, Canada. Electronic address: James.Howard@lhsc.on.ca.
⁴ Occupational Health and Safety Services, London Health Sciences Centre, London, Canada. Electronic address: richard.rosedale@lhsc.on.ca.

PMID: 24721460
DOI: 10.1016/j.joca.2014.03.018

Abstract

Objective: To compare measurement properties of the P4 pain scale, Western Ontario and McMaster Universities Arthritis Index pain subscale (WOMAC-pain), and Intermittent and Constant Osteoarthritis Pain (ICOAP) measure in patients with knee osteoarthritis (OA).

Design: A secondary analysis from a randomized controlled trial included participants (n = 156) with knee OA that were consulting with a surgeon regarding knee arthroplasty. They completed pain measures (P4, WOMAC-pain, ICOAP) and WOMAC-function subscale (WOMAC-function) at baseline and 2 weeks. Measurement properties assessed in various subgroups included floor/ceiling effects, test-retest reliability using intraclass correlation coefficients (ICC2,1), internal consistency using Cronbach's ɑ, factorial structure of each pain measure combined with WOMAC-function using principal component analysis, and responsiveness using standardized response mean (SRM).

Results: P4 had low floor and ceiling effects (<1%). P4 test-retest reliability (ICC2,1 = 0.72), internal consistency (Chronbach's ɑ = 0.91), and responsiveness (SRM = 0.56) were similar to the values for WOMAC-pain and ICOAP. Factorial structure of P4 and ICOAP were separate from WOMAC-function items. WOMAC-pain and WOMAC-function items loaded on similar factors. ICOAP-constant subscale had a large floor effect (33%).

Conclusions: P4 should be used to measure pain in patients with knee OA. It had acceptable measurement properties which is comparable to more widely used pain measures. WOMAC-pain shared a factorial structure with WOMAC-function indicating these measures might be capturing the same construct, questioning its validity to measure pain separately from function. ICOAP had acceptable properties. More work should compare pain measures in less severely affected OA populations.

Keywords: Intermittent and Constant Osteoarthritis Pain; Knee osteoarthritis; P4; Reliability; Western Ontario and McMaster Universities Arthritis Index.

Publication types

Comparative Study
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Aged
Aged, 80 and over
Arthroplasty, Replacement, Knee / methods
Chronic Pain / physiopathology*
Disability Evaluation*
Female
Humans
Male
Middle Aged
Ontario
Osteoarthritis, Knee / diagnosis*
Osteoarthritis, Knee / surgery
Pain Measurement / methods*
Patient Selection
Reproducibility of Results
Sensitivity and Specificity
Severity of Illness Index
Sickness Impact Profile