Background/Purpose: Enthesitis constitutes one of the CASPAR stem criteria for the classification of psoriasis arthritis, however as enthesitis may be clinically silent many psoriatic patients may have unnoticed enthesitis and may in fact have silent psoriatic arthritis. Objective: To determine the prevalence of enthesitis by PDUS examination in a cohort of psoriatic patients without a diagnosis of PsA. To determine the agreement between clinical exploration and ultrasound results, and the prevalence of “silent” disease according to CASPAR criteria.

Methods: Descriptive and observational cross-sectional study of 122 patients referred from the primary care with cutaneous psoriasis without arthritis, 20 healthy subjects were used as controls. The entheseal examination was performed by the MASES plus lateral and medial epycondile, quadriceps tendon, proximal and distal patella and plantar aponeuroses. PDUS was performed in longitudinal and transverse multiplanar examination (Logiq 5 PRO; General Electric Healthcare, Kyunnggi-do, Korea), using multifrequency linear array transducers (7–12 MHz) in the following enthesis: lateral and medial epycondile, quadriceps tendon, proximal and distal patella, aquilles tendon plantar aponeuroses. Active enthesitis was defined by the presence of thickness or altered echogenecity as well as the presence of vascularisation. Intraobserver realiability was verified by blindly assessed the stored baseline images 3 months after the real time examination. Prevalence of enthesitis between psoriatic patients and controls was compared with the chi-squared test. Considering PDUS results as the gold standard, sensitivity, specificity and predictive values of clinical exploration were estimated. Agreement was evaluated with the Kappa index.

Results: 107 psoriatic patients had both clinical and PDUS examination performed. 10.3% (n=11) of the patients had clinical enthesitis, whereas 70.1% (n=75) of psoriatic patients and 45% (n=9) (p=0.030; OR=2.86) of controls had PDUS findings of present or past enthesitis. 37.4% (n=40) of psoriatic patients and 5% (n=1) of controls had active enthesitis by PDUS criteria (p=0.003; OR=11.34). Agreement between clinical exploration and PDUS to identify present enthesitis was low (Kappa index=0.182). Only 8 of the 40 patients with active enthesitis in PDUS had clinical enthesitis. Considering PDUS results as the gold standard, clinical findings showed a sensitivity of 20% (95% CI: 6.3-33.6%), specificity 95.5% (95% CI: 89.8%-100%), positive predictive value 72.7% (95% CI: 41.9%-100%), negative predictive value 66.7% (95% CI: 56.7%-76.6%). By applying CASPAR criteria, 8 (8.7%) patients would have a diagnosis of PsA based on clinical enthesitis, whereas 22 (23.9%) would have, by PDUS, a diagnosis of silent entheseal PsA.

Conclusion: The prevalence of PDUS enthesopathy in psoriatic patients without psoriatic arthritis is high, 70.1%. There is not a good agreement between clinical and PDUS findings. If active enthesitis, although clinically silent, is considered only by PDUS definitions, 23.9% of patients would meet CASPAR criteria in this study

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-enthesitis-in-psoriatic-patients-agreement-between-clinical-and-power-doppler-ultrasonography-exploration-and-its-implications-for-the-classification-of-psoriatic-arthritis/