THU0439 MEASUREMENT PROPERTIES OF PAIN CATASTROPHIZING SCALE IN PATIENTS WITH KNEE OSTEOARTHRITIS

Abstract

Background: Up to 20% of patients with knee osteoarthritis (OA) do not respond well to knee replacement surgery (KR) despite surgical success. We hypothesize that pain catastrophizing among these patients may affect KR outcomes. Objectives: To assess the validity and reliability of the Pain Catastrophizing Scale (PCS) in patients with knee osteoarthritis (OA) in Singapore. Methods: We used cross-sectional data from 675 knee OA patients enlisted for knee replacement surgery (KR) in a Singapore tertiary referral hospital from May to September 2018. Data was collected 2 weeks prior to KR. Analyses were guided by the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) framework. Internal consistency was assessed using Cronbach’s alpha. Construct validity was assessed through seven a priori hypotheses by correlation of overall PCS score with other patient-reported outcomes. Structural validity was evaluated via confirmatory factor analysis using maximum likelihood method. Measurement invariance across gender subgroups was assessed using multi-group confirmatory factor analysis. Results: There were 675 patients (mean±SD age = 65.52±6.84 years, 70.37% female) with knee OA enlisted for KR (91.7% total, 8.3% unicompartmental). The mean±SD PCS score was 12.65±10.55, 0.14% and 8.63% ceiling and floor effects. PCS demonstrated high internal consistency (Cronbach’s alpha=0.94). Construct validity was demonstrated by fulfilment of six out of seven (85%) a priori hypotheses. The PCS model showed good fit for a two-factor structure after accounting for appropriate modification indices (CFI=0.957, TLI=0.950, RMSEA=0.073, SRMR=0.043), demonstrating good structural validity. Measurement invariance across gender groups was demonstrated. Conclusion: This study supports internal consistency, construct validity and structure validity of PCS as a measure of pain catastrophizing in knee OA patients in Singapore. ** p Disclosure of Interests: Wei Jie Ong: None declared, Yu Heng Kwan: None declared, Julian Thumboo: None declared, Seng Jin Yeo: None declared, William Yeo: None declared, Ying Ying Leung Grant/research support from: Abbvie, Novartis, Speakers bureau: Abbvie and Novartis, Speakers bureau: Novartis