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

Background : Ultraviolet-induced fluorescent dermoscopy (UVFD) is not a new imaging technique; however, its clinical utility in nail disorders has been largely underrecognized. Recent interest in this modality has highlighted its potential diagnostic applications, which remain to be fully established. This study aimed to characterize UVFD signs and patterns in nail psoriasis and onychomycosis and to investigate whether its integration with conventional dermoscopy (CD) improves diagnostic accuracy in differentiating the two. 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.背景：紫外线诱导荧光皮肤镜（ultraviolet-induced fluorescent dermoscopy, UVFD）并非一项新兴成像技术，但其在甲病中的临床应用价值长期未得到充分重视。近年来学界对该成像手段的关注凸显了其潜在的诊断应用价值，但相关结论仍有待全面验证。本研究旨在明确甲银屑病与甲真菌病的UVFD特征性体征及成像模式，并探讨将其与常规皮肤镜（conventional dermoscopy, CD）联合使用是否可提升二者的鉴别诊断准确率。方法：本项多中心前瞻性对照研究共纳入6家甲病专科中心的108例患者，其中甲真菌病患者63例，甲银屑病患者45例。研究采用DermLite DL5型设备开展标准化甲皮肤镜（甲镜检查，onychoscopy）检查，沿用既定术语体系，并通过3次专家线上会议明确UVFD相关体征的定义。诊断效能评估采用卡方检验或Fisher确切概率法、多变量logistic回归及受试者工作特征（ROC）曲线分析。结果：UVFD检测中，深部荧光与淡黄色荧光的出现与甲真菌病显著相关；反之，点状荧光模式则更倾向于提示甲银屑病。CD-UVFD联合模型的曲线下面积（AUC）达0.981（95%置信区间：0.962~1.000），而单独采用常规皮肤镜检测的AUC为0.973（95%置信区间：0.948~0.997），单独采用UVFD检测的AUC为0.821（95%置信区间：0.742~0.900）。结论：UVFD是一项极具前景的辅助成像手段，可作为常规皮肤镜的补充用于甲病的评估。CD-UVFD联合模型的诊断区分度数值上高于单独常规皮肤镜检测，但该差异未达到统计学显著性水平。UVFD可增强甲甲板改变及甲剥离范围的可视化效果，或可帮助临床医师为疑似甲真菌病患者选择最佳的真菌学采样部位。未来需开展进一步的前瞻性研究以验证本研究结果、评估观察者间重现性，并明确UVFD辅助诊断对临床决策的影响。