Psoriatic arthritis (PsA) affects choice of biologic agents. Guidelines have recently been published from the American College of Rheumatology/National Psoriasis Foundation (ACR/NPF) on PsA [1], with a few caveats regarding axial disease, inflammatory bowel disease, and joint destruction. It is important for dermatologists to screen for PsA and refer to rheumatologists when appropriate.

• Patients with PsA have a different range of possible treatments than non-PsA patients.
• Clinicians assessing patients for psoriasis should consider severity and affected areas, past medical history, comorbidities, past treatments and their efficacy, and patient preferences regarding treatment for a shared decision making approach.
• Factors such as risk, efficacy, speed, convenience, and insurance/financial burden are considered.
• For patients with PsA, further factors must be taken into consideration.

PsA is a heterogeneous disease with a spectrum of clinical manifestations. Determining which biologic is best suited for a particular patient depends upon the phenotypic manifestation, which can include the following:

• DIP joint involvement
• Symmetric arthritis
• Asymmetric oligoarthritis
• Spondylitis
• Dactylitis
• Enthesitis.

It is important to select a biologic therapy that will positively affect both conditions. The degree of skin and joint severity should both be considered. Consultation and referral to a rheumatologist is recommended.

• PsA is prevalent, affecting up to 30 % of patients.
• Screening is important because a delayed diagnosis contributes to poorer long-term outcomes including joint erosions which are irreversible.
• Consultation with and referral to a rheumatologist is often important.
• Dermatologists have a responsibility to screen patients for PsA, according to new psoriasis guidelines [1].
• The GRAPPA (Group for Research and Assessment of Psoriasis and Psoriatic Arthritis) App is one available method, as is the PEST score, with no single method considered the definitive method for PsA screening.
• When working in conjunction with a rheumatologist, the dermatologist is expected to make a determination as to the presence of psoriasis.

• Biologic options for PsA patients with psoriasis include: etanercept, adalimumab, infliximab, certolizumab, secukinumab, ixekizumab, and ustekinumab.
• If PsA is confirmed in a psoriasis patient, and the patient is treatment naive, the first line of treatment should be a tumor necrosis factor (TNF) inhibitor. There are several caveats, for example, an oral systemic can be used for patients who prefer oral treatment. If severe psoriasis is present, a different class can be considered. TNF inhibitors may be contraindicated.
• The SPIRIT-H2H trial compared ixekizumab versus adalimumab, finding that patients treated with ixekizumab were more likely to achieve primary endpoints of 100% skin clearance according to the Psoriasis Area and Severity Index (PASI 100) and ACR 50 at 24 weeks.

Treatment caveats include the following:

• Axial disease is not synovitis, is not assessed in ACR score, does not respond to methotrexate and responds differently to other biologics. First line treatments are NSAIDs and physical therapy, followed by TNF inhibitors and IL-17 inhibitors.
• The target should be remission or inactive disease, and the appropriate measures should be very low disease activity (VLDA), which includes PASI and BSA assessments [2].

• The GRAPPA produces very complex guidelines that are difficult to apply in clinical practice.
• Recently published ACR/NPF guidelines for the treatment of psoriatic arthritis [1] are useful.
• The ACR/NPF guidelines are based upon literature in conjunction with GRADE evidence, developed by stakeholders including dermatologists, rheumatologists, other health professionals, and patients.
• The guidelines are based upon three endpoints: ACR scores, Health Assessment Questionnaire-Disability (HAQ) index, and safety.
• Joint destruction was not a basis for the guidelines [1].
• Overall, when considering HAQ, TNF inhibitors are generally considered better, and not considered worse in terms of safety, with the caveat that more head-to-head studies are needed.