Background/Purpose:  Ultrasound evaluation of synovitis and enthesitis has changed the management of rheumatic diseases. In the present study we compare Power Doppler (PD) and Spectral Doppler (sD) ultrasonography indices (semiquantitative gray scale and PD scores and resistance index (RI) in the nails of patients with psoriatic arthritis (PsA) and their controls. Potential associations between sD measurements and clinical parameters were also investigated^1,2,3.

Methods: A cross sectional study was done and 44 patients with PsA, if they fulfilled the CASPAR criteria, 10 healthy controls and 6 patients with hands osteoarthritis (OA) were enrolled. Clinical parameters were recorded while US evaluation was performed in patients and controls nails. Nail bed measurements and semiquantitative gray scale (GS) and PD scores were derived for all nails examined, while RI was measured using sD. 

Results: Statistically significant lower RI was found in patients with PsA as compared to their controls (p<0.001). RI measurements in our sample presented high sensibility and specificity for PsA. Area under the ROC curve was 0.858 (p<0.01).   Choosing a cut off point of 0.395 for RI measurements, the test indicates that RI values below 0.4 are associated with 100% sensitivity and 96% specificity for entheseal inflammatory activity. Lower RI was observed even in PsA patients with no symptom of nail involvement. GS and PD semiquantitative scores were also significantly higher in PsA patients as compared to their controls (p<0.05). ROC analyzes demonstrated that RI measurements using sD presented high sensibility and specificity for PsA.

Conclusion:  Nail sD indices are significantly different in PsA patients independently on the presence of clinically evident nail involvement. These sD parameters might find a place in early diagnosis, monitoring of disease activity and response to therapy in PsA patients.

References:

1. Gutierrez M, Filippucci E, et al. A sonographic spectrum of psoriatic arthritis: “the five targets”. Clin Rheumatol. 2010; 29(2): 133–142.
2. Terslev L, Torp-Pedersen S, Qvistgaard E, von der Recke P, Bliddal H. Doppler ultrasound findings in healthy wrists and finger joints. Ann Rheum Dis 2004; 63:644–648.
3. Mendonça JA, Nogueira JP, Laurido IMM, Vierhout C, et al. Can spectral doppler identify nail enthesitis in psoriatic arthritis? Annals of the Rheumatic Diseases 2014; 73(2):1-1332.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/high-specificity-of-spectral-nail-assessment-in-psoriatic-arthritis-patients/