Background Several patient-reported outcome (PRO) instruments have been administered in ongoing clinical trials to capture the symptoms and impact of systemic lupus erythematosus (SLE) patients' experience. Pain has been recognized as an important manifestation of SLE. The Brief Pain Inventory-Short Form (BPI-SF) was developed to assess the severity of pain and the impact of pain on daily functions in the adult population.
Objectives The goal of this observational study was to evaluate the psychometric properties of the BPI-SF in patients with moderate-to-severe SLE.
Methods Participants were recruited using a free electronic medication-monitoring service. Patients ≥18 years who self-reported a physician diagnosis of SLE (confirmed by medical record review) and active SLE demonstrated by a Systemic Lupus Activity Questionnaire (SLAQ) score of ≥11 (0-44 scale) were included. BPI-SF and Short Form (36) Health Survey (SF-36) were administered in electronic format at baseline, week 2, and week 12. Psychometric properties of the BPI-SF and items and domains were evaluated by standard statistical techniques.
Results A total of 122 patients were included. The mean age was 45.7 years; 95.9% were female; and 68.9% were non-Hispanic white. Cronbach's alpha were >0.9 for all BPI-SF items. Test-retest reliability of the BPI-SF showed a stable correlation for item #7 (Intraclass Correlation Coefficient 0.79), while all other items and domain correlations were above 0.5. The BPI-SF domain and global scores were moderately positively correlated to the SLAQ score (all correlations r>0.4), but they were negatively correlated to the SF-36 Bodily Pain domain (r<-0.6). The BPI-SF domain and global scores were moderately negatively correlated to the SF-36 Physical Function domain and Physical Component scores, with low correlations between the pain severity domain and SF-36 Mental Component scores (r=-0.16). The BPI-SF item #3 (worst pain) was moderately positively correlated to the SLAQ score (r=0.49). Patients who self-reported inactive or less active disease activity (SLAQ <29) scored lower on domain and global scores (p<0.05) and item #3 (p<0.0001), compared to patients who self-reported active disease activity (SLAQ ≥29). The findings suggested all BPI-SF domain scores and item #3 were able to differentiate between patients with less severe or more severe pain.
Conclusions Assessment of pain intensity, as measured by the BPI-SF, demonstrated validity and reliability in a sample of patients with SLE and may be used as a PRO tool in clinical trials.
Acknowledgements This research was funded by Eli Lilly and Company, Indianapolis, IN.
Disclosure of Interest A. Naegeli Shareholder of: Eli Lilly and Company, Employee of: Eli Lilly and Company, S. Al Sawah Shareholder of: Eli Lilly and Company, Employee of: Eli Lilly and Company