Psychometric properties of the Persian version of the pain anxiety symptom scale (PASS-20) in chronic non-specific neck pain patients

Abstract

Objectives Pain-related anxiety has been linked to avoidance behaviour, maintenance of pain and disability. A valid and reliable tool is required to evaluate pain-related anxiety among Persian speaking adults with chronic non-specific neck pain (CNSNP). This study aimed to evaluate psychometric properties of the Persian pain anxiety symptom scale-20 (PASS-20) according to the consensus-based standards for the selection of health measurement instruments (COSMIN) checklist in Iranian adults with CNSNP. Methods 198 individuals with CNSNP completed the PASS-20. The factorial structure (confirmatory factor analysis (CFA), exploratory factor analysis (EFA)), test-retest reliability (intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC)), internal consistency (Cronbach’s alpha), and construct validity (convergent and known-group validity) were assessed. The correlation between PASS-20 with pain catastrophizing scale (PCS), Tampa Scale for Kinesiophobia (TSK), neck disability index (NDI), Beck Depression Inventory (BDI), visual analog scale (VAS) (Spearman’s rank correlation) were examined. Known-group validity of PASS-20 was evaluated by comparing the difference between the PASS-20 scores of the known groups based on level of disability, pain intensity and gender using non-parametric tests. Results The CFA showed almost the best fit with the original version. The subscales and total score demonstrated good internal consistency (Cronbach’s α: 0.70–0.92) and high test-retest reliability (ICC: 0.94–0.97). PASS-20 had significant moderate correlations with PCS, TSK, NDI, VAS and a significant low correlation with BDI. Regarding known-group validity, the total score of Persian PASS-20 was higher in CNSNP with higher levels of pain and disability and in the female gender. Conclusions The Persian PASS-20 has acceptable psychometric properties in adults with CNSNP. The results of the factor analysis supported the four-factor structure comparable to the original version. Ethical Committee number 921672004.