Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Measuring Pain in Systemic Sclerosis: The Short-Form McGill Pain Questionnaire or a Single Item Measure of Pain? A Confirmatory Factor Analysis.

Baalbaki1,  Ghassan El, Lober2,  Janie, Hudson4,  Marie, Baron1,  Murray, Thombs3,  Brett D., Canadian Scleroderma Research Group (CSRG),  

Jewish General Hospital, Montreal, QC, Canada
McGill University
McGill University, Montreal, QC, Canada
McGill University and Jewish General Hospital

Background:

Pain is common in patients with systemic sclerosis (SSc), and severity levels are comparable to other rheumatic diseases. Patients with SSc report a number of painful symptoms. Existing studies of pain in SSc have used a variety of pain assessment tools, including a single-item pain Visual Analog Scale (VAS), a pain numerical rating scale (NRS), and the longer 15-item short-form McGill Pain Questionnaire (MPQ-SF). OMERACT 6 reported that the pain VAS is valid to measure pain related to Raynaud's phenomenon and digital ulcers in SSc, but has not been examined as a general pain measure. VAS and NRS measures have been shown to function similarly in other patient groups. Despite being longer, the MPQ-SF would be a potentially attractive measure if it were to demonstrate more robust validity characteristics than single-item measures or if it were able to differentiate between sensory and affective components of pain, as has been suggested in some patient groups. The objectives of this study were (1) to assess whether the MPQ-SF has stronger validity characteristics among patients with SSc compared to two single-item measures, the pain NRS and the Present Pain Index (PPI), a single Likert item, and (2) to determine whether the MPQ-SF differentiates meaningfully between sensory and affective components of pain in SSc patients.

Methods:

Patients with SSc were recruited from the Canadian Scleroderma Research Group Registry. To assess convergent validity compared to the NRS and PPI, Pearson's correlations, with 95% confidence intervals (CIs), were computed between the MPQ-SF, NRS, and PPI with other outcome measures, including the Center for Epidemiologic Studies Depression scale (CES-D), the Health Assessment Questionnaire – Disability Index (HAQ-DI), and the Mental andd Physical Component Summaries(MCS and PCS) scores of the Short-Form 36 Health Survey Questionnaire. To assess the degree that the MPQ-SF differentiated between sensory and affective factors, confirmatory factor analysis (CFA) models were conducted using MPlus, treating items as ordinal data. In addition, Pearson's correlations with 95% CIs of sensory and affective factor scores with CES-D, the HAQ-DI, the MCS and PCS were calculated to test for differences between the sensory and affective correlations.

Results:

A total of 1,091 patients were included. The MPQ-SF, NRS and PPI correlated similarly to all other outcome measures with no significant or substantive differences. Model fit for the two-factor model (sensory and affective) was good (c2(55) = 198.3, P < 0.001; CFI = 0.97, TLI = 0.99, RMSEA = 0.05), but a single-factor model that did not differentiate sensory and affective pain fit similarly well (c2(54) = 234.2, P < 0.001; CFI = 0.96, TLI = 0.99, RMSEA = 0.06). Sensory and affective factor scores correlated similarly with other outcome measures.

Conclusion:

The MPQ-SF did not improve on the PNRS or PPI as a measure of pain in SSc. In addition, no evidence was found that the MPQ-SF provides substantively different assessment of sensory and affective pain. The PNRS is a reliable and valid measure of pain in SSc, and is advantageous for use because of its brevity in administration and scoring.

To cite this abstract, please use the following information:
Baalbaki, Ghassan El, Lober, Janie, Hudson, Marie, Baron, Murray, Thombs, Brett D., Canadian Scleroderma Research Group (CSRG), ; Measuring Pain in Systemic Sclerosis: The Short-Form McGill Pain Questionnaire or a Single Item Measure of Pain? A Confirmatory Factor Analysis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2247
DOI: 10.1002/art.30010

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