Ultrasound-aided diagnosis of preclinical phases of psoriatic arthritis in biologic-naïve psoriasis patients with or without arthralgia.

OBJECTIVES: The evolution of psoriasis (PsO) to psoriatic arthritis (PsA) has been proposed recently. There are three phases that occur in sequence prior to classifiable PsA: PsO patients, PsO patients with a positive imaging, and PsO patients with arthralgia not explained by other diagnosis. The purpose of this study was to compare the differences among preclinical phases using ultrasound and clinical assessment. METHODS: Patients with psoriasis were recruited. Patients who had been previously diagnosed with psoriatic arthritis or who had used biologics were excluded. A 52-joint ultrasound (52j US) assessment and clinical assessments including the swollen joint count, tender joint count, erythrocyte sediment rate, C-reactive protein, dactylitis score, enthesitis score, psoriasis severity, and nail psoriasis severity, were performed. RESULTS: A total of 188 eligible psoriasis patients were enrolled. Physical examination revealed 39 patients (20%) with at least one swollen joint. The 52j US assessment demonstrated 90 patients (47%) having at least one joint with grey-scale score 2-3. All patients were further stratified into PsO patients (n=58), PsO patients with a positive imaging, (n=59), PsO patients with arthralgia not explained by other diagnosis (n=27), and classifiable PsA (n=39). There were no differences in clinical characteristics other than tender joint count found among the three preclinical phases of PsA. Dactylitis score, swollen joint count and heatly assessment questionnaire score were significantly higher in classifiable PsA. CONCLUSIONS: Nearly half of the psoriasis patients without previously diagnosed psoriatic arthritis would be classified into the preclinical phases of psoriatic arthritis based on the 52j US and clinical assessments. Ultrasound assessment is helpful for identifying psoriasis patients who are in the preclinical phases of psoriatic arthritis, particularly for those without arthralgia.