Cross-cultural adaptation and validation of the Norwegian pain catastrophizing scale in patients with low back pain.

BACKGROUND: Pain catastrophizing has been found to be an important predictor of disability and days lost from work in patients with low back pain. The most commonly used outcome measure to identify pain catastrophizing is the Pain Catastrophizing Scale (PCS). To enable the use of the PCS in clinical settings and research in Norwegian speaking patients, the PCS had to be translated. The purpose of this study was therefore to translate and cross-culturally adapt the PCS into Norwegian and to test internal consistency, construct validity and reproducibility of the PCS.

METHODS: The PCS was translated before it was tested for psychometric properties. Patients with subacute or chronic non-specific low back pain aged 18 years or more were recruited from primary and secondary care. Validity of the PCS was assessed by evaluating data quality (missing, floor and ceiling effects), principal components analysis, internal consistency (Cronbach's alpha), and construct validity (Spearman's rho). Reproducibility analyses included standard error of measurement, minimum detectable change, limits of agreement, and intraclass correlation coefficients.

RESULTS: A total of 38 men and 52 women (n = 90), with a mean (SD) age of 47.6 (11.7) years, were included for baseline testing. A subgroup of 61 patients was included for test-retest assessments. The Norwegian PCS was easy-to-comprehend. The principal components analysis supported a three-factor structure, internal consistency was satisfactory for the PCS total score (α 0.90) and the subscales rumination (α 0.83) and helplessness (α 0.86), but not for the subscale magnification (α 0.53). In total, 86% of the correlation analyses were in accordance with predefined hypothesis. The reliability analyses showed intraclass correlation coefficients of 0.74 - 0.87 for the PCS total score and subscales. The PCS total score (range 0-52 points) showed a standard error of measurement of 4.6 points and a 95% minimum detectable change estimate of 12.8 points.

CONCLUSIONS: The Norwegian PCS total score showed acceptable psychometric properties in terms of comprehensibility, consistency, construct validity, and reproducibility when applied to patients with subacute or chronic LBP from different clinical settings. Our study support the use of the PCS total score for clinical or research purposes identifying or evaluating pain catastrophizing.