This prospective multicentre study seeks to compare the diagnostic performance of a dermatologist-based screening and referral strategy with a questionnaire-based approach in identifying patients with a high likelihood of Psoriatic Arthritis (PsA) among those with psoriasis.

The study will include patients with psoriasis who have not been previously evaluated for PsA. Those with psoriasis but presenting new musculoskeletal symptoms will also be eligible. Patients will undergo a two-step screening process at the dermatologist level:

1. Questionnaire-Based Screening: Patients will complete the PEST questionnaire. Those scoring ≥3 out of 5 points will be labeled "PEST-positive" and eligible for referral.
2. Dermatologist-Based Evaluation: Independently of PEST results, dermatologists will perform standardized musculoskeletal assessments, including evaluation for peripheral arthritis, enthesitis, dactylitis, and back pain. Dermatologists will be blinded to PEST outcomes and specially trained to perform the required MSK evaluations.

PEST-positive and/or physician-positive patients will be referred to a rheumatologist for further evaluation. Rheumatologists will conduct thorough assessments, including demographic data, clinical history, family history, patient-reported outcomes, and physical examinations. The presence of PsA and the confidence level in diagnosis will be recorded.

The primary outcome will be the proportion of patients diagnosed with PsA using different approaches. Subgroups will be analysed based on PEST and physician evaluations, allowing for a detailed comparison of diagnostic strategies. The study will also evaluate the agreement between dermatologists and rheumatologists on the presence of musculoskeletal manifestations.

A total of 500 patients will be referred to rheumatologists for evaluation, which will require up to 1,000 psoriasis patients to be screened by dermatologists. The study will involve collaboration between dermatology and rheumatology centres, with an anticipated 50 pairs of dermatology-rheumatology centres (or clusters including more than one dermatology centre).

COMPOSITION will recruit competitively. However, to ensure a balanced study population, the number of patients included in a rheumatology centre will be limited to 30, with up to 60 patients recruited per country. Each dermatology centre is expected to screen 20-40 patients with psoriasis over a six-month recruitment period, referring about 10-20 eligible patients to a partnered rheumatology centre. We plan to select up to 50 dermatology-rheumatology pairs/clusters. Study centres will receive a pre-specified case-based reimbursement and a study start-up fee. Institutional overhead costs of up to 25% can be reimbursed if not waived.

Authorship and Compensation Guidelines for Study Participation

Participation in this study offers several opportunities for recognition and support:

Authorship Eligibility:

National coordinators are eligible for authorship.
Top recruiters who are not national coordinators will also be considered for authorship.
A group authorship model is being planned, ensuring all recruiting Principal Investigators (PIs) are associated with the study in PubMed.

Administrative Overhead Compensation:

Some institutions require overhead payments to cover administrative costs (e.g., at Charité Hospital, 25% of funds are allocated to administrative expenses, with the remaining 75% directed to the investigator).
While we aim to minimize overhead costs, we are prepared to compensate up to 25% when unavoidable.
These guidelines are designed to recognize the contributions of participating investigators while addressing institutional requirements transparently.