Evaluating psychometric properties of the Short Form Brief Pain Inventory Sinhala Version (SF BPI-Sin) among Sinhala speaking patients with cancer pain in Sri Lanka

BACKGROUND: Pain is one of the most common and unpleasant symptoms of patients with cancer. The Short Form Brief Pain Inventory (SF-BPI), has been psychometrically validated in several languages and widely used globally. Availability of a validated pain tool in Sinhala is a current requirement enabling the use among the majority of Sinhala-speaking cancer patients in Sri Lanka. The purpose of the study was to evaluate the psychometric properties of Sinhala translated version of SF BPI. METHODS: The translation was done by forward–backward translation method. Content and face validity were evaluated by a panel of experts and patients with cancer pain respectively. The study included 151 participants with cancer pain, registered at the Pain Clinic, Apeksha Hospital, Sri Lanka. The reliability, discriminant and convergent validity were assessed. The confirmatory factor analysis (CFA) was conducted and evaluated the two factor (severity, interference) and three factor models (severity, affective/ activity interference). In the three factor model-1, item ‘sleep’ was included within the affective interference along with mood, relationship with others and enjoyment of life. In the three factor model-2, item ‘sleep’ was included within the activity interference along with general activities, walking and normal works. Ethical approval was obtained from the Ethics Review Committee, Faculty of Medical Sciences, University of Sri Jayewardenepura, Sri Lanka. RESULTS: A total of 151 participants (79 males, 72 females) with a mean age of 54.6 (+/− 13.2) years were included. The composite reliability (0.902, 0.879), average variance extracted (AVE) (0.647, 0.568) and Cronbach’s alpha (0.819, 0.869) calculated for each severity and interference subscales were acceptable. The discriminant validity assessed with the heterotrait-monotrait criterion was 0.18. According to the Fornell–Larcker criterion, the square root of AVE of severity and interference factors (0.804, 0.753) greater than the correlation between the factors (0.140) demonstrated the discriminant validity. The CFA supported the three-factor model-2 (CFI—0.959, SRMR—0.0513, RMSEA—0.0699) and the values for two-factor and three-factor model-1 were marginally acceptable. CONCLUSIONS: The Sinhala version of SF BPI is a reliable and valid instrument for the assessment of cancer pain among Sinhala speaking patients in Sri Lanka.