Dimensionality, reliability, and validity of the Finnish version of the pain catastrophizing scale in chronic low back pain.

Objectives: The 13-item pain catastrophizing scale (PCS) is the most commonly used measure of pain catastrophizing. A validated Finnish version of the PCS has previously been unavailable. The objectives were to translate the original English version of the PCS into Finnish (PCS-FI), then to evaluate (i) structural validity of the PCS-FI with a confirmatory factor analysis (CFA), (ii) internal reliability with Cronbach's alpha, Omega, and Omega hierarchical, (iii) convergent validity with measures of well-being, quality of life, sleep quality, symptoms of central sensitization, and anxiety, and (iv) known-groups validity between participants with chronic low back pain (CLBP) and pain-free controls.

Methods: The translation process was performed with established guidelines. The PCS-FI was psychometrically validated using 92 participants with CLBP and 53 pain-free controls.

Results: Structural validity with CFA supported a bifactor solution. However, low reliability was found for the three specific factors (ω _h ranging from 0.14 to 0.18) compared to the general factor (ω _h = 0.88) suggesting that only the total score should be used. Convergent validity analysis showed satisfactory correlations and medium effect sizes with the other patient-reported outcome measures. Participants with CLBP had significantly higher total PCS-FI scores than pain-free controls.

Conclusions: The PCS-FI appears to be a valid and reliable instrument for assessing pain-related catastrophizing in Finnish-speaking populations. Ethical approval for this study was obtained from the Research Ethics Committee of the Northern Savo Hospital District, identification number 2131/2022, on the 31st of January 2022.