Conventional and Ultraviolet-Induced Fluorescence Dermoscopy for the Diagnosis of Onychomycosis and Nail Psoriasis

Methods

This multicenter, prospective, comparative study included 108 patients (63 with onychomycosis, 45 with nail psoriasis) across 6 centers specializing in nail disorders. Standardized nail dermoscopy (onychoscopy) was conducted using a DermLite DL5 device. Established terminology was used, while UVFD signs were defined after 3 expert virtual meetings.

Diagnostic performance was assessed using chi-square or Fisher's exact tests, multivariable logistic regression, and receiver operating characteristic (ROC) curve analysis. Results: On UVFD, the presence of deep fluorescence and yellowish fluorescence were significantly associated with onychomycosis. Conversely, a dotted fluorescence pattern favoured nail psoriasis.

The combined CD-UVFD model achieved an area under the curve (AUC) of 0.981 (95% CI: 0.962-1.000), compared with 0.973 for CD alone (95% CI: 0.948-0.997) and 0.821 for UVFD alone (95% CI: 0.742-0.900). Conclusion: UVFD represents a promising adjunctive imaging modality to complement CD in the evaluation of nail disorders. The combined CD-UVFD model showed numerically higher diagnostic discrimination than CD alone, although the difference was not statistically significant.

UVFD may enhance the visualization of nail plate alterations and the extent of onycholysis, and could potentially assist clinicians in selecting the most appropriate site for mycological sampling in suspected onychomycosis. Further prospective studies are warranted to validate these findings, assess interobserver reproducibility, and determine the impact of UVFD-assisted diagnosis on clinical decision-making.