Ultrasound Assessment of Psoriatic Arthritis Patients With Clinically Normal Nails and Evaluation of its Correlation With the Disease Activity: A Case-Control Study.

Objectives: Nail unit is one of the targets of ultrasound (US) assessment. We aimed to compare ultrasound parameters of clinically normal nail unit in psoriatic arthritis (PsA) patients with healthy controls (HC) and evaluate their correlations with disease activity.

Methods: This was a cross-sectional study including patients with PsA and matched HC. Tender (TJC) and swollen joint count (SJC), Psoriasis Area and Severity Index (PASI), and Disease Activity in Psoriatic Arthritis (DAPSA) were collected in PsA patients. Patients underwent US assessment of fingernails with a study of morphological changes and measurement of the thickness of nail bed (NBT), nail plate (NPT), and adjacent skin (ST). Correlation between nail unit parameters and disease activity was studied.

Results: We evaluated 22 PsA patients (219 nails) and 21 HC (210 nails). Mean DAPSA was 21.56 ± 14.36 and mean PASI was 2.19 ± 3.8. PsA patients had more US morphological changes than HC (16.89 vs 3.33%, P = .03). NPT comparison between identical fingernails of PsA and HC did not reveal significant difference. However, NBT was significantly higher in HC (1.77 vs 2.07 mm, P = .027) as well as ST (2.26 vs 2.59 mm, P = .003). TJC and ST were positively correlated (r = .46, P = .03). No correlation was noted between disease activity scores and NPT, NBT, or ST in PsA patients. In biologic parameters, ESR was negatively correlated with ST (r = -.41, P = .05).

Conclusions: Nail bed and adjacent skin US morphological changes were contributive to distinguish psoriatic from healthy nails. Adjacent skin thickness measurement was positively correlated with TJC and ESR, suggesting that it could be used as an indicator of disease activity in PsA.