What are the laboratory tests for Psoriatic Arthritis (PsA)?

From the Guidelines

Laboratory tests for psoriatic arthritis should include erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess inflammation levels, as recommended by the Annals of the Rheumatic Diseases in 2009 1. When evaluating patients with psoriatic arthritis, it is essential to consider the following lab tests:

• Erythrocyte sedimentation rate (ESR) to measure inflammation levels
• C-reactive protein (CRP) to assess inflammation levels
• Complete blood count (CBC) to check for anemia of chronic disease
• Uric acid levels to rule out gout
• Joint fluid analysis to exclude infection or crystal arthropathies
• Imaging studies like X-rays, MRIs, or ultrasounds to show characteristic joint changes These tests help establish diagnosis, monitor disease activity, and guide treatment decisions. According to the study published in the Annals of the Rheumatic Diseases in 2009 1, baseline evaluations of PsA should include assessments of peripheral joint tenderness and swelling, pain, patient global assessment of disease activity, physical function, health-related quality of life, fatigue, and acute phase reactants. The study also highlights the importance of radiographic assessment, which can help identify factors associated with a poor prognosis, such as the number of actively inflamed joints, elevated ESR, and diminished quality of life 1.

From the Research

Psoriatic Arthritis Lab Tests

• Laboratory tests are used to diagnose and manage psoriatic arthritis (PsA), but their limitations should be understood 2.
• Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies are commonly used to diagnose rheumatoid arthritis (RA), but can also be present in PsA patients 3, 4, 5, 6.
• The presence of anti-CCP antibodies in PsA patients has been associated with:
  • More severe disease 5, 6
  • Polyarticular disease pattern 5
  • Higher frequency of treatment with biologics 5
  • Lower frequency of treatment with classic disease-modifying drugs 5
  • Shorter survival of methotrexate monotherapy and first-line biotechnological drugs 6
• The prevalence of anti-CCP antibodies in PsA patients varies across studies, ranging from 12.2% to 12.5% 3, 5.
• RF and anti-CCP antibodies can be detected in the serum of some PsA patients, and their presence may indicate a more aggressive disease course 4, 5, 6.
• Laboratory tests, including RF and anti-CCP antibodies, should be interpreted in the context of clinical symptoms and other diagnostic criteria to accurately diagnose and manage PsA 2, 3, 4, 5, 6.