Validation of the PROFAD-SSI-SF in Patients with Primary Sjögren's Syndrome with Organ Involvement: Results of Qualitative Interviews and Psychometric Analyses

Introduction The Profile of Fatigue and Discomfort–Sicca Symptoms Inventory–Short Form (PROFAD-SSI-SF) is a 19-item patient-reported outcome (PRO) measure to assess pain, fatigue, and dryness in patients with primary Sjögren’s syndrome (pSS). This analysis identified concepts important to measure, and evaluated the content validity and measurement properties of the PROFAD-SSI-SF, in patients with pSS. Methods Qualitative analyses (GSK Study 208396) used transcripts from an online concept elicitation (CE) discussion forum with patients with pSS and interviews with key opinion leaders (KOLs) to finalize a disease model depicting important concepts for patients with pSS. Cognitive debriefing (CD) interviews with patients with pSS were conducted to further evaluate the content validity of the PROFAD-SSI-SF. Quantitative analyses (GSK Study 213253) used post hoc analyses of blinded data from a phase 2 trial to assess PROFAD-SSI-SF measurement properties. Results The CE discussion forum ( N = 46) revealed dryness (oral 87.0%, ocular 73.9%, cutaneous 37.0%, vaginal 23.9%, nasal 15.2%, otic 6.5%), pain (89.1%), and fatigue (87.0%) as the most reported symptoms. KOLs ( N = 5) found the concepts identified in the disease model accurate and understandable, and confirmed that PROs used in pSS studies should focus on dryness, joint pain, and fatigue. In the CD interviews ( N = 20), of the 19 participants asked, all found the PROFAD-SSI-SF easy to understand, and 14/19 items were considered relevant by ≥ 18/20 participants. The quantitative analyses found an acceptable fit of the PROFAD-SSI-SF factor structure, with adequate internal consistency, test–retest reliability, convergent validity with other PRO measures, known-groups validity with Patient Global Assessment, and ability to detect change in patients with pSS. Conclusion The final disease model confirmed that the PROFAD-SSI-SF assesses concepts that are relevant and important to patients with pSS. Our findings support the content validity and measurement properties of the PROFAD-SSI-SF as a fit-for-purpose PRO measure appropriate for use in clinical trials in patients with pSS. Clinical Trial Registration number for the phase 2 trial Clinicaltrials.gov NCT02631538