There are no laboratory tests that are specific for psoriatic arthritis. Acute phase reactants such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) may become elevated, as they do in most inflammatory diseases, and are markers of severe disease. Patients with psoriatic arthritis typically have lower levels of ESR and CRP than patients with rheumatoid arthritis. However, a normal ESR and CRP does not rule out a diagnosis of psoriatic arthritis.
Patients with psoriatic arthritis are typically seronegative for rheumatoid factor, although it is detected in 5%-9% of cases. Negative rheumatoid factor is often seen in psoriatic arthritis. Antinuclear antibody titers in persons with psoriatic arthritis typically are no different from those of age- and sex-matched controls.
Learn more about the diagnosis of psoriatic arthritis.
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Cite this: Herbert S. Diamond, Eric M. Ruderman, Marina Magrey. Fast Five Quiz: Psoriatic Arthritis Presentation and Diagnosis - Medscape - Jan 25, 2023.