Rasch Analysis of the Italian version of Pain Catastrophizing Scale (PCS-I)

OBJECTIVE: The aim of this study was to investigate the psychometric properties of the Italian version of the Pain Catastrophizing Scale (PCS-I) in patients with chronic low back pain. METHODS: In a cross sectional study a total of 150 subjects with chronic low back pain were included. The Italian translation of the PCS was administered to all subjects. The properties of the Italian version of the PCS were explored by a Rasch analysis. RESULTS: The PCS-I, by means of few modifications, fitted the Rasch model and passed the independent t-test for a unidimensional scale. The response categories for item 2 I fell I can't go on needed to be collapsed from 4 to 3 levels. Only the item 7 I keep thinking to of other painful events showed fit residual that exceeded the chosen thresholds of +/- 2.5. No Differential functioning (DIF) was observed for age, sex, marital status, BMI and smoking. CONCLUSION: The Italian version of PCS, with the purposed modifications, seems to reflect a unidimensional construct of Pain Catastrophizing. The scale seemed to be quite robust across age, sex, marital status, BMI and smoking. Targeting of the scale was moderate. A raw score to metric conversion was proposed.