A multicenter case-control study for early detection of psoriatic arthritis using ultrasonography and easy-to-use questionnaires in psoriasis patients in the outpatient dermatology clinic

Psoriasis (PsO) is a chronic skin disorder with a prevalence of approximately
2-3% in the Western population. Between 6 and 42% of patients with psoriasis
will develop psoriatic arthritis (PsA), a chronic inflammatory rheumatic
disorder. Increasing evidence suggests that diagnosing PsA early and
subsequently providing early treatment, improves patients* outcomes
substantially. Since in the majority of cases the symptoms of the skin precede
the musculoskeletal symptoms, an opportunity for screening arises at outpatient
dermatology clinics. However, it is difficult for physicians treating patients
with psoriasis, e.g. dermatologists, to discriminate musculoskeletal symptoms
caused by PsA from other causes of musculoskeletal symptoms. A standardised
screening (zorgpad) at the dermatology outpatient clinic could enhance the
early identification of PsO patients having PsA. An easy to use questionnaire
and ultrasonography, could be valuable tools for such a standardised screening.

To study PsO patients in the outpatient dermatology clinic in order to 1) to
compare the sensitivity and specificity of the easy to use questionnaire: the
Psoriasis Epidemiology Screening Tool (PEST) and ultrasonography in identifying
PsO patients having PsA 2) to evaluate the value of screening with the PEST and
with ultrasonography for relevant patient health outcomes

Prospective observational cohort study with a nested case-control study

In total, all PsO patients will be scheduled for one initial study visit and
for an additional study visit if they have positive PEST score (meaning risk
for PsA) in the follow-up. Visits as well as the collection of data will be as
much as possible integrated with regular patient care. The additional
measurements are questionnaires, ultrasound of entheses and painful joints, and
additional blood samples (±80 mL). All patients will be discussed with a
rheumatologist and the patients having PsA at baseline will be referred to the
rheumatologist for further treatment. A large benefit for the participating PsO
patient is the possible earlier identification of PsA with subsequent earlier
treatment.