Outcome domains reported by patients, caregivers, healthcare professionals and stakeholders for calcium pyrophosphate deposition (CPPD): A content analysis based on semi-structured qualitative interviews from the OMERACT CPPD working group

Introduction: Although calcium pyrophosphate deposition (CPPD) disease is common, there are no validated outcome measures for clinical research in this condition. The aim of this study was to generate a list of outcome domains as reported by patients, their caregivers, healthcare professionals (HCPs) and stakeholders to inform the development of an Outcome Measures in Rheumatology (OMERACT) Core Domain Set for CPPD. Methods: Patients with CPPD and their caregivers, HCPs and stakeholders took part in semi-structured qualitative interviews to explore potential outcome domains for CPPD clinical research relevant to their lived experience and knowledge of CPPD. Interviews were conducted in six countries across three continents. Data was analysed using manifest content analysis to identify outcome domains, which were tabulated and mapped to the core areas as defined by the OMERACT Filter 2.1. Results: Thirty-six interviews were conducted in total. Participants comprised of 28 patients (six of which included a caregiver), seven HCPs and one stakeholder. The commonly identified (sub-) domains (d) across the 1) abnormalities/manifestations core area were joint pain (d = 35), joint swelling (d = 27), joint stiffness (d = 25), CPPD flares (d = 25); 2) life-impact core area were overall function (d=35), and specifically the ability to complete daily tasks (d = 25); and 3) societal/resource use core area were use of analgesic medicines (d = 26). Patients more commonly reported joint swelling, stiffness and range of movement, and use of analgesics while HCPs more commonly reported domains relating to presence of CPP crystals, radiologic calcification, joint damage, time to diagnosis and suitability of treatment. Conclusion: Among a number of potential outcome domains identified, articular manifestations, function and analgesic use were most frequently mentioned by participants. These findings will be used to develop an OMERACT Core Domain Set for CPPD.