The purpose of this study is to obtain patient and stakeholder perspectives on what outcome measures should be included in future trials on CPPD (Calcium PyroPhosphate Deposition), a common form of inflammatory arthritis. This will form part of a wider OMERACT (Outcome Measures in Rheumatology) study, involving multiple international sites, to determine a core domain set (an agreed set of outcome measures) for this disease.

In the UK, up to 10 patients with CPPD and their caregivers, healthcare professionals who care for patients with CPPD, and other stakeholders, which may include government organisations, non-government organisations, pharmaceutical representatives and health advocacy groups, will be invited to participate in a single, semi-structured interview.

Interviews will be face-to-face or telephone, last up to one hour and digitally audio-recorded. For patients and their caregivers, interviews will explore their lived experience of CPPD, its impact on their daily lives, and the perceived relevance of outcome measures used in previous studies. For healthcare professionals and other stakeholders, interviews will explore their experience dealing with patients with CPPD, how they perceive CPPD impacts patient lives, and the perceived relevance of the outcome measures used in previous studies.

Following analysis of the data, participants will be sent a short report with the researchers' findings, and asked to check the accuracy of these and provide brief written feedback.

Interviews will also take place with patients, caregivers, healthcare practitioners and stakeholders at the other international sites where ethics committee approval will be sought locally. It is anticipated that around 30 participants will be recruited across all sites. Analysis of all interviews will be primarily conducted and managed at the UK site.

Inclusion Criteria:

Patients:

• People with a diagnosis of CPPD of any form and/or their caregiver (includes acute CPP crystal arthritis (pseudogout), chronic CPP crystal arthritis, crowned dens syndrome, and osteoarthritis with CPPD)
• Ability to give informed consent
• Age over 18 years

Healthcare professionals:

• A healthcare professional (nurse, GP or hospital doctor) who cares or has cared for patients with CPPD

Other stakeholders:

• Government organisations, non-government organisations, pharmaceutical representatives and health advocacy groups

Exclusion Criteria:

• Dementia
• Terminal illness
• Unable to give informed consent
• Stroke with receptive or expressive dysphasia
• Severe enduring mental illness
• Autoimmune rheumatic disease such as rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, gout
• Total joint replacement in the previous 3 months

Patients with CPPD, healthcare practitioners who work with patients with CPPD, and stakeholders who work on behalf of those with CPPD