Findings from serologic testing can point to RA in the differential diagnosis of PsA. RF, cyclic citrullinated peptide antibodies (anti-CCP), erythrocyte sedimentation rate, and C-reactive protein are commonly measured in patient evaluations for arthritis. Approximately 80% of patients with RA have an elevated RF titer; approximately 70% have an elevated anti-CCP level, although these are not necessarily the same patients. Elevations in erythrocyte sedimentation rate or C-reactive protein level may be seen in PsA, but these values are more likely to be elevated and to higher degrees in RA.
Although nearly all patients with PsA are RF- and/or CCP-negative, PsA cannot be eliminated from the differential on the basis of CCP- and/or RF-negative status alone.
Learn more about laboratory studies in workup of PsA.
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Cite this: Eric M. Ruderman. Fast Five Quiz: How Much Do You Know About Psoriatic Arthritis? - Medscape - Dec 23, 2021.