Psoriatic Arthritis Screening in Patients with Psoriasis
All patients with psoriasis should be screened for psoriatic arthritis at every visit by asking about morning joint stiffness, joint swelling, and enthesitis, with immediate rheumatology referral for any suspicious symptoms. 1
Why Screening Matters
Early detection of PsA is critical because uncontrolled arthritis causes irreversible joint damage in over 50% of patients, and skin disease precedes arthritis in 73% of cases—often by many years. 1 The prevalence of PsA among psoriasis patients ranges from 30-33%, making this a common and serious comorbidity that directly impacts morbidity and quality of life. 1
What to Screen For at Every Visit
Ask these specific questions:
- Morning joint stiffness lasting ≥30 minutes (particularly if ≥60 minutes, which strongly suggests inflammatory arthritis) 1, 2
- Joint swelling that is visible or palpable (not just pain alone—actual synovitis is essential for diagnosis) 1, 2
- Dactylitis (sausage-like swelling of fingers or toes) 1
- Heel pain or other enthesitis symptoms (pain at tendon/ligament insertion sites) 1
- Nail changes (pitting, onycholysis, oil spots) which associate strongly with PsA, especially when distal interphalangeal joints are involved 3
Physical Examination Findings
When time permits, examine for:
- Joint swelling, redness, warmth, and tenderness (signs of active inflammation) 1
- Dactylitis (entire digit swelling) 1
- Enthesitis (tenderness at Achilles insertion, plantar fascia, lateral epicondyle) 1
- Nail dystrophy (pitting, onycholysis, subungual hyperkeratosis) 1, 3
Screening Tools: Limited Clinical Utility
While several validated screening questionnaires exist—including the Toronto Psoriatic Arthritis Screen (TOPAS), Psoriasis Epidemiology Screening Tool (PEST), and Psoriatic Arthritis Screening and Evaluation (PASE)—these tools have performed poorly when tested outside their original development populations and have limited usefulness in routine clinical practice. 1, 4
The PASE questionnaire showed 76-82% sensitivity and 73-76% specificity with a cutoff score of 44-47, but requires validation in broader community settings. 5, 6
When to Refer to Rheumatology
Refer immediately (ideally within 6 weeks) if any of the following are present: 1
- Morning stiffness ≥60 minutes PLUS visible/palpable joint swelling in ≥2 joints 2
- Positive "squeeze test" (pain with lateral compression of metacarpophalangeal or metatarsophalangeal joints) 2
- Dactylitis 1
- Inflammatory back pain (chronic pain >3 months, age <45 at onset, improves with exercise but not rest, awakens patient in second half of night) 2
CASPAR Criteria for Diagnosis
The simplest diagnostic approach uses the CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria, which require established inflammatory articular disease plus ≥3 points from: 1, 4
- Current psoriasis (2 points)
- History of psoriasis (1 point)
- Family history of psoriasis (1 point)
- Dactylitis (1 point)
- Juxta-articular new bone formation on radiographs (1 point)
- Rheumatoid factor negativity (1 point)
- Nail dystrophy (1 point)
Critical Pitfalls to Avoid
Do not wait for radiographic changes—joint damage occurs early and is irreversible. 1 Early aggressive treatment prevents permanent joint destruction. 1
Do not dismiss arthralgia without objective swelling as "just osteoarthritis." Morning stiffness ≥60 minutes distinguishes inflammatory from mechanical causes, and inflammatory arthritis improves with movement and NSAIDs, not opioids. 2
Do not assume all joint pain in psoriasis patients is PsA. Differentiate from osteoarthritis (stiffness <30 minutes, worse with activity, older age, DIP/PIP/thumb base involvement) and fibromyalgia (widespread pain without objective swelling). 1, 2
Patient Education
Inform all psoriasis patients about the association between psoriasis and PsA (Strength of Recommendation B). 1 Instruct them to report any new musculoskeletal symptoms immediately, particularly morning joint stiffness or swelling. 1
Additional Comorbidity Screening
Patients with PsA have significantly elevated cardiovascular risk (1.3-1.6× higher rates of hypertension, ischemic heart disease, peripheral vascular disease, and cerebrovascular disease). 1 Screen for cardiovascular risk factors including blood pressure, BMI, waist circumference, fasting lipids, and fasting glucose according to American Heart Association guidelines. 1
Screen for depression as psoriasis patients have double the odds of clinical depression (OR 1.99,95% CI 1.53-2.59). 7
Treatment Implications
The presence of PsA fundamentally changes therapeutic approach. Patients with both psoriasis and PsA require systemic therapy that addresses both domains—biologics targeting TNF-α or IL-17/IL-23 pathways are preferred as they treat both skin and joint disease effectively. 8, 9, 4 Traditional DMARDs like methotrexate have not demonstrated ability to slow radiographic progression of PsA, whereas anti-TNF agents and IL-17 inhibitors have proven efficacy. 4, 10