Potential Use of Optical Coherence Tomography and High-Frequency Ultrasound for the Assessment of Nail Disease in Psoriasis and Psoriatic Arthritis

Background: Psoriatic nail disease is increasingly recognised to be of major clinical and research relevance. Clinical assessment remains the current gold standard for its evaluation. Objective: We compared optical coherence tomography (OCT) and ultrasound (US) for nail disease assessment in psoriatic disease. Methods: 18 patients with at least one involved nail and 12 healthy controls were scanned using OCT; psoriatic patients also had an US scan (using a linear probe at 9-14 MHz). Nail and contour abnormalities were documented. Clinical onychopathy was scored independently using the modified Nail Psoriasis Severity Index. Results: Among 180 nails, 67.8% had clinical findings whereas 33.9% were abnormal by US and 44.4% had abnormalities on OCT. A positive OCT had a sensitivity and specificity of 44.4 and 95.8%, respectively, with a positive likelihood ratio of 10.7 for nail disease. OCT demonstrated 76.3% absolute agreement compared with clinical assessment and 65% with US. OCT detected subtle abnormalities in 12 clinically normal nails and in 41 nails with normal US findings. Conclusion: These findings show that OCT has a potential for the systematic characterisation of psoriatic nail changes and could be useful in diagnosis and more objective assessment of treatment response.