Evaluation of Subclinical Hand Joint Synovitis by Ultrasonography in Patients with Psoriatic Arthritis and Cutaneous Psoriasis: A Case-Control Study.

Objectives: To find the frequency of subclinical hand joint synovitis (SS) in patients with psoriatic arthritis (PsA) and cutaneous psoriasis (PsC) compared to healthy controls (HC), and correlation of SS with disease activity.

Methods: PsA patients (n= 52), without any past/current history of hand joint arthritis, PsC patients (n= 48), and 45 HC were recruited. Grey-scale and power Doppler Ultrasonography of bilateral hand joints were performed. The proportions of hand joints with SS were estimated in each group. A wrist-ray score was devised. Correlations were obtained between the number of joints with SS and disease activity parameters.

Results: Higher proportion of PsA patients (55.8%) had SS than PsC (29.2%, p= 0.007), and HC (22.2%, p=0.001). Proportion of joints with SS was higher in PsA patients (5.38%) compared to PsC (2.92%, [p=0.0008]), and HC (1.11%, [p=0.0007]). Compared to HC, PsA patients had significantly higher bilateral ray 3 (p=0.002 and 0.01 for left and right ray 3, respectively), and right ray 4 involvement (p=0.037) and PsC patients had higher left ray 3 involvement (p=0.03). Wrist-ray score above 2.5 could distinguish patients of PsC with significant subclinical synovitis compared to controls (area under curve: 0.857, 95% confidence interval: 0.71-1.00). There was a significant correlation of SS with ESR in PsA group (p-value: 0.044), and with CRP in PsC group (p-value: 0.003), but not with other disease activity indices.

Conclusion: SS was noted in approximately half of PsA and 1/3 of PsC patients. Both PsA and PsC patients had a significantly higher number of hand joint SS than HC. Ray pattern of hand joint SS could be present in both PsA and PsC.