What are the diagnostic criteria and treatment options for psoriatic arthritis?

Diagnosing Psoriatic Arthritis

Psoriatic arthritis diagnosis relies on the CASPAR criteria, which require established inflammatory articular disease plus at least 3 points from a 7-feature scoring system, with current psoriasis weighted most heavily at 2 points. 1

Diagnostic Workflow

Step 1: Confirm Inflammatory Musculoskeletal Disease

Before applying CASPAR criteria, you must first establish inflammatory articular disease, defined by: 1

• Tender and swollen joints on examination 1
• Prolonged morning stiffness 1
• Immobility-induced stiffness 1
• Joint, spine, and/or entheseal pain associated with erythema, warmth, and swelling 1

Step 2: Apply CASPAR Scoring System (Need ≥3 Points)

The validated CASPAR criteria demonstrate 98.7% specificity and 91.4% sensitivity: 1

Current psoriasis (2 points):

• Active psoriatic skin or scalp lesions confirmed by examination 1

Personal history of psoriasis (1 point):

• Only counted if current psoriasis is absent 1

Family history of psoriasis (1 point):

• Only counted if no current psoriasis and no personal history 1

Typical psoriatic nail dystrophy (1 point):

• Onycholysis, pitting, or hyperkeratosis 1

Current or historical dactylitis (1 point):

• Swelling of entire digit recorded by rheumatologist 1

Juxta-articular new bone formation (1 point):

• Seen on plain radiographs of hands or feet 1, 2

Rheumatoid factor negativity (1 point):

• Determined by any method except latex; ELISA preferred 1

Step 3: Essential Clinical Features to Assess

Enthesitis screening should include palpation of: 3

• Lateral epicondyle of the humerus 3
• Medial condyle of the femur 3
• Achilles tendon insertion 3

Inflammatory back pain features (suggesting axial involvement): 3

• Early morning stiffness 3
• Pain relieved by exercise and exacerbated by rest 3

Laboratory Assessment

There are no diagnostic laboratory markers for PsA—diagnosis relies primarily on clinical criteria. 4

Mandatory Baseline Tests

• ESR and CRP: The only laboratory tests specifically recommended by OMERACT 8 consensus guidelines for baseline PsA evaluation 4
• These assess inflammation severity, not diagnosis 4

Exclusionary Testing

• RF and anti-CCP antibodies: Order to exclude rheumatoid arthritis, especially in polyarticular presentations 4
• The presence of RF or anti-CCP does not preclude PsA diagnosis but should prompt careful diagnostic scrutiny 3

Baseline Assessment for All Suspected PsA

Comprehensive joint assessment: 2

• 68 joints for tenderness 2
• 66 joints for swelling 2

Patient-reported measures: 2

• Pain on visual analogue scale 2
• Patient global assessment of disease activity 2
• Physical function (Health Assessment Questionnaire) 2
• Health-related quality of life (SF-36 or PsAQoL) 2
• Fatigue assessment 2

Imaging: 2

• X-rays of hands and feet at baseline for all suspected inflammatory arthritis 3
• Radiographic assessment according to clinical manifestation and physician judgment 2

Prognostic Factors Requiring Aggressive Treatment

Poor prognosis indicators that should trigger earlier biologic therapy: 2, 4

• Polyarticular disease (versus monoarticular) 2
• Elevated ESR at baseline 2, 4
• Failure of previous medication trials 2
• Presence of joint damage clinically or radiographically 2
• Diminished functional status by HAQ 2
• Reduced quality of life by SF-36, DLQI, or PsAQoL 2

Critical Timing Considerations

Any patient with suspected inflammatory arthritis and a six-week history of painful, swollen joints should be referred for specialist assessment. 3

• Approximately 20% of patients develop PsA before psoriasis, often many years before skin or nail changes 3
• At least 40% develop radiographically detectable joint destruction 5
• Erosions are present in nearly 50% at 10 years of disease 6
• Early diagnosis and treatment substantially improve long-term prognosis 3

Treatment Approach

First-Line Peripheral Arthritis Treatment

NSAIDs and intra-articular glucocorticoid injections: 2

• Appropriate for initial symptom management 2

Systemic corticosteroids are NOT recommended: 2

• Not typically used in psoriasis treatment 2
• Only advisable in discrete circumstances, not for chronic use 2
• Risk of post-steroid psoriasis flare 2

DMARD Therapy

DMARDs have potential to reduce or prevent joint damage, though none proven specifically in PsA. 2

DMARD failure definition: 2

• At least one DMARD failed individually or in combination 2
• Adequate trial = >3 months treatment, with >2 months at standard target dose 2
• Unless significant intolerance or toxicity limits the dose 2

Combination therapy: 2

• No evidence for combination therapy, but can be used in patients who fail single agent 2
• Consider in those with joint damage progression despite treatment 2

Biologic Therapy (TNF Inhibitors)

TNF inhibitors are indicated for: 2, 7

• DMARD failures 2
• Patients with poor prognostic factors 4
• Polyarticular disease with elevated inflammatory markers 4

Available TNF inhibitors with proven efficacy: 7

• Etanercept 8, 7
• Infliximab 7
• Adalimumab 7
• Golimumab 7
• Certolizumab 7

These agents effectively slow radiographic progression of joint disease, unlike traditional DMARDs. 7

Response Assessment

Treatment failure is defined as: 2

• Lack of acceptable clinical improvement despite appropriate therapy duration and dose 2
• Evidence of progression of joint damage on radiographs 2

Response criteria for peripheral arthritis: 2

• DAS28 (reliable and discriminative in PsA) 2
• EULAR response criteria 2
• ACR20/50/70 percentage response criteria 2

Medications to Avoid

Do NOT use in PsA: 2

• Gold salts 2
• Chloroquine 2
• Hydroxychloroquine 2