Abstract: Objective: To investigate the application of dermoscopy and fluorescent staining in the diagnosis of onychomycosis. Methods: The patients with suspected onychomycosis from January 2021 to December 2022 in Hebei central hospital of petro China were selected as the study subjects. Nail clippings were collected and examined by direct potassium hydroxide (KOH) microscopy, dermoscopy, and fluorescent staining. The results of dermatoscopy, fluorescent staining and KOH direct microscopy were statistically analyzed. The clinical subtypes and dermatoscopy characteristics of onychomycosis patients were analyzed. The diagnostic value of dermatoscopy and fluorescent staining for onychomycosis was analyzed by receiver operating characteristic curve (ROC). Results: Among 98 patients with suspected onychomycosis, 86 cases (87.76%) were diagnosed as onychomycosis according to dermoscopy images, and 84 cases (85.71%) were diagnosed as onychomycosis according to fluorescence staining. One hundred and sixty five nails in 87 cases were positive for KOH direct microscopic examination, including 85 (51.52%) of distal lateral subungual type, 38 (23.03%) of total nail damage type and 42 (25.45%) of white superficial type. Dermoscopic images showed that cone-shaped nail keratosis in 25 nails which were all the total nail damage type, longitudinal striated in 41 nails, of which 21 (51.22%) were longitudinal striated, distal lateral serrated margin in 106 nails, of which 74 were distal lateral subungual type (69.82%). The AUC value, sensitivity, specificity, positive predictive value, negative predictive value and accuracy of dermoscope and fluorescence staining in the diagnosis of onychomycosis were 94.25% and 90.80%, 63.64% and 54.55% , 95.35% and 94.05%, 58.33% and 42.86%, 90.82% and 86.73%, respectively, with no significant differences of those between dermoscopy and fluorescence staining (Ps>0.05). Conclusions: Dermoscope and fluorescent staining can be used as auxiliary clinical diagnostic methods for onychomycosis, and the main characteristics of dermoscopy in patients with onychomycosis are conical nail keratosis, longitudinal stripe nail destruction and serrated edge distal lateral subungual type.

Key words: onychomycosis, dermatoscope, fluorescence staining