Fast Five Quiz: Psoriatic Arthritis Presentation and Diagnosis

Herbert S. Diamond, MD; Eric M. Ruderman, MD


December 23, 2021

Elevations of ESR, markers of inflammation, are common among patients with psoriatic arthritis. But while increased ESR is a hallmark of the disease, a normal ESR cannot be used to rule out a diagnosis. In patients with psoriatic arthritis, an ESR greater than 15 mm/h, along with medication use before the first clinical visit, evidence of radiologic damage, and absence of nail lesions, has been associated with increased mortality. Elevated ESR and CRP levels are considered markers of severe PsA by the American College of Rheumatology (ACR)/National Psoriasis Foundation.

While most patients with RA have positive findings for RF, patients with psoriatic arthritis are usually seronegative for RF, though it is detected in a small percentage (5%-9%) of patients. However, because testing is associated with a high false-positive rate, RF-positive and RF-negative patients should receive the same treatment.

Antinuclear antibody titers in persons with psoriatic arthritis are no different from those of age- and sex-matched controls. Low levels of circulating immune complexes have been discovered in 56% of patients with psoriatic arthritis, but they do not appear to influence disease activity.

Laboratory studies are important both in the initial diagnosis and monitoring of psoriatic arthritis. The most characteristic laboratory abnormalities are elevations of the ESR and C-reactive protein level. The results from these laboratory tests help to monitor disease activity by measuring inflammation.

Learn more about the diagnosis of psoriatic arthritis.


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