To what extend is nail ultrasound discriminative between psoriasis, psoriatic arthritis and healthy subjects?

To assess the discriminative utility of nail features detected by B-mode (BM) and color Doppler (CD) ultrasound (US) between patients with psoriasis (PsO) and psoriatic arthritis (PsA) and healthy controls. Sixty patients with PsA, 21 patients with PsO, and 20 healthy controls were prospectively included. All patients underwent a dermatologic assessment and PsA patients also a rheumatologic assessment. All patients and controls underwent a US assessment of the finger nails that included a BM score for nail plate integrity and four different CD scores based on the amount and location of CD signals in the nail bed/matrix. In addition, we measured the thickness of the nail bed (TNB) and nail plate (TNP). The BM score and the CD score based on the amount of signals in the nail bed in contact with the ventral plate discriminated between the control group (median, range 0.0, 0–4 and 2.0, 0–9, respectively) and the PsO/PsA group (median, range: 7.0, 0–31 and 5.14, 0–13, respectively) (p < 0.05) with or without clinical nail involvement. The CD scores based on the percentage of the nail bed/matrix occupied by Doppler signals did not discriminate between controls and PsO/PsA patients. TNB and TNP were significantly higher in psoriatic nails with or without clinical involvement than in control nails. In PsO/PsA patients, the BM score, TNB and TNP were significantly higher in clinically involved nail than in clinically non-involved nails. Our results showed discriminative utility of BM US and some CD US features for PsO/PsA nails.