Detection of Demodex in rosacea: standardized skin surface biopsy vs. ultraviolet dermoscopy.

BACKGROUND

Demodex mites are believed to contribute to the pathogenesis of both rosacea and demodicosis. While standardized skin surface biopsy (SSSB) remains the gold standard for detecting Demodex density, it is invasive and time-consuming. Ultraviolet (UV) dermoscopy, a noninvasive technique that visualizes fluorescent structures, may offer a rapid alternative for identifying Demodex proliferation.

OBJECTIVES

To investigate the relationship between Demodex folliculorum and Demodex brevis counts obtained by SSSB and fluorescent dots detected under UV dermoscopy, and to evaluate the diagnostic value of these findings in rosacea and demodicosis.

METHODS

Fifty-four patients with rosacea or demodicosis were evaluated using both UV dermoscopy and SSSB from the same facial region. Orange and bright blue fluorescent dots were recorded dermoscopically, and mite density and species were quantified via SSSB. Correlation analyses and receiver operating characteristic (ROC) curve analysis were performed to assess diagnostic performance.

RESULTS

A significant positive correlation was found between total Demodex count and bright blue fluorescent dots (r = 0.343; P = 0.013), but not with orange dots (r = -0.065; P = 0.649). Only D. folliculorum showed significant correlation with blue and total fluorescent dots. ROC analysis identified > 11 bright blue dots as the optimal threshold for predicting Demodex positivity, with a sensitivity of 82.1% and specificity of 71.4% (area under the curve 0.793; P = 0.003).

CONCLUSIONS

Bright blue fluorescent dots observed under UV dermoscopy correlate significantly with Demodex density, particularly D. folliculorum. A threshold of > 11 blue dots demonstrated good diagnostic accuracy and may serve as a practical, noninvasive alternative or adjunct to SSSB in clinical settings. Orange fluorescence was not associated with Demodex density and most likely reflects unrelated sebaceous or microbial activity.