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Commentary: Early Diagnosis of PsA, February 2023

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Vinod Chandran, MBBS, MD, DM, PhD

Most patients develop psoriatic arthritis (PsA) after the onset of cutaneous psoriasis. The path toward long-term remission of PsA may be by early diagnosis and effective treatment prior to the onset of joint damage. Recently published research has focused on these concepts. Nonspecific manifestations of musculoskeletal (MSK) inflammation make early diagnosis difficult. Fluorescence-optical imaging (FOI), a method using fluorescent dyes and a camera, can identify areas with vascular changes and inflammation and may detect early signs of MSK inflammation. In a prospective observational cohort study including 389 patients with plaque psoriasis who were at risk for PsA (nail psoriasis, MSK symptoms), Koehm and colleagues report that PsA was diagnosed in 50% (36% by clinical examination [CE] by rheumatologists and 14% by MSK ultrasonography [MSUS]). An additional 30% were positive on FOI of the hands. At a 2-year follow up, the incidence rate of PsA was higher among patients positive on FOI but negative on CE (11.8%) compared with previously published incidence rates. Thus, rheumatologists should carefully evaluate and follow up such higher risk psoriasis patients to identify PsA early. Established imaging modalities such as MSUS and MRI, and novel tools such as FOI, could facilitate early PsA diagnosis.

Appropriate assessment of MSK symptoms and signs by dermatologists may lead to more appropriate referral to rheumatologists. MSUS is being increasingly explored for early identification of PsA. A handheld, chip-based ultrasound device (HHUD) is a novel promising instrument that can be easily implemented in clinical practice. In a prospective study including 140 patients with psoriasis who presented to dermatologists with arthralgia. Grobelski and colleagues screened for PsA using medical history, CE, and the German Psoriasis Arthritis Diagnostic PsA screening questionnaire (GEPARD) paired with MSUS examination of up to three painful joints by trained dermatologists. Nineteen patients (13.6%) were diagnosed with PsA by rheumatologists. Interestingly, in 45 of the 46 patients the preliminary diagnosis of PsA was revised to "no PsA" after MSUS. The addition of MSUS changed the sensitivity and specificity of early PsA screening strategy from 88.2% and 54.4% to 70.6% and 90.4%, respectively. The positive predictive value increased to 56.5% from 25.4% after MSUS. Thus, the use of a quick MSUS using HHUD may lead to more accurate referral to rheumatologists. The challenge is seamless integration of MSUS into busy dermatology practices.

The goal of PsA treatment is to achieve a state of remission or low disease activity. Criteria for minimal disease activity (MDA) have been established. Achieving MDA leads to better health-related quality of life (HRQOL), as well as less joint damage. In a prospective cohort study that included 240 patients with newly diagnosed disease-modifying antirheumatic drug-naive PsA, Snoeck Henkemans and colleagues demonstrate that failure to achieve MDA in the first year after the diagnosis of PsA was associated with worse HRQOL and health status, functional impairment, fatigue, pain, and higher anxiety and depression. Compared with patients who achieved sustained MDA in the first year after diagnosis, those who did not achieve MDA had higher scores for pain, fatigue, and functional ability and higher anxiety and depression during follow-up, which persisted despite treatment intensification. Thus, implementation of treat-to-target strategies with the aim of achieving sustained MDA within 1 year of diagnosis is likely to have better long-term benefits in this lifelong disease.

Another study emphasized the need for early treatment to improve long-term outcomes. In a post hoc analysis of two phase 3 trials including 1554 patients with PsA who received 300-mg or 150-mg secukinumab with or without a loading dose, Mease and colleagues showed that high baseline radiographic damage reduced the likelihood of achieving MDA.

Overall, these studies indicate that early diagnosis and treatment prior to developing joint damage with the aim to achieve sustained MDA within a year will lead to better long-term outcome for patients with PsA.

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Fluorescence-optical imaging may detect preclinical PsA
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