Spanish cross-cultural adaptation and psychometric validation of the graded chronic pain scale revised for fibromyalgia

Background

Chronic widespread pain represents one of the cornerstones in the definition of fibromyalgia. Pain severity can be measured through different instruments, among which the Graded Chronic Pain Scale represents an outstanding framework to assess pain. Its revised version (GCPS-R) has been recently created to adhere to the new paradigmatic definition of chronic pain. Despite the relevance and clinical impact of the GCPS-R, its validation into Spanish has not been performed yet.

Objectives

To develop a cross-cultural Spanish-language adaptation of the GCPS-R in a sample of patients diagnosed with fibromyalgia. Besides, we aimed to carry out an initial psychometric analysis of the questionnaire in this population.

Methods

An observational, prospective, longitudinal study was conducted among a sample of subjects with fibromyalgia. The translation and cross-cultural adaptation of the GCPS-R was performed, and the new version of the instrument was administered to patients with fibromyalgia. Construct validity was assessed by means of factor analysis, whilst internal consistency, convergent validity, and test–retest reliability were also performed.

Results

The sample analyzed consisted of 224 subjects overall. Factor 1 displayed a Cronbach's alpha of 0.711, whilst Factor 2 had an alpha value of 0.890. The convergent validity analysis performed on the pain-intensity subscale of the instrument yielded statistically significant and strong correlation coefficients (Pearson's r = 0.713; p-value < 0.001). Test–retest reliability yielded weighted Cohen's Kappa scores of 0.537 (p-value < 0.001).

Conclusion

The GCPS-R-SP represents a simple, easy to administrate, and clinically efficient measure with favorable psychometric properties, covering the level and the impact of chronic pain in subjects with fibromyalgia.