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

Abstract

Plain Language Summary Primary Sjögren’s syndrome (pSS) is a disease where the immune system attacks the body, causing a number of symptoms, most notably dryness (sicca) of the eyes and mouth. The Profile of Fatigue and Discomfort–Sicca Symptoms Inventory–Short Form (PROFAD-SSI-SF) is a questionnaire for patients with pSS that asks about their symptoms. This paper evaluates how relevant the PROFAD-SSI-SF questions are to patients with pSS, and how consistently and accurately the questionnaire can measure changes in their symptoms. We reviewed information about the symptoms and impacts of pSS from an online discussion forum for patients with pSS. Patients said that dryness, fatigue, and pain were the symptoms that most affected their day-to-day lives and well-being. We combined this information with previous research on pSS to design a diagram explaining the key symptoms and day-to-day impacts of pSS, which was reviewed by five experts in pSS. In doing so, we aimed to confirm whether the most important things to patients about living with pSS are asked in the PROFAD-SSI-SF questionnaire. Next, we asked 20 patients with pSS how easy they found the PROFAD-SSI-SF to complete and if any important concepts were missing; they reported that the PROFAD-SSI-SF was easy to fill in and that the important questions were included. Finally, we looked at data from a clinical trial that used the PROFAD-SSI-SF and found it accurately measures changes in symptoms of patients with pSS. This means that the PROFAD-SSI-SF could be used in clinical trials to help assess new medicines for pSS.

Keywords

• Autoimmune disease
• Content validity
• Instrument validation
• Patient-reported outcomes
• Primary Sjogren’s syndrome
• PROFAD-SSI-SF