The efficacy of a new superficial needle-scraping (SNS) method for assessing Demodex mite density in papulopustular rosacea (PPR) has support from study data published in the Journal of Cosmetic Dermatology.
Investigators recruited 40 patients with PPR and 35 control individuals with acne vulgaris from the National Cheng Kung University Hospital in Taiwan. SNS was performed by gently scraping five small pustules on participants’ faces, using the convex surface of an 18# needle. The ability of SNS to distinguish between high-Demodex-density PPR and low-Demodex-density acne was quantified by receiver operating characteristic curve analysis. Standardized skin surface biopsy was also performed in patients with PPR; Demodex densities obtained via SNS and standardized skin surface biopsy were compared. Demodex density was expressed as mites per 5 pustules for SNS.
Demographic characteristics were similar among patients and control individuals, with no statistically significant differences in sex and age composition. The SNS technique identified Demodex mites in 83.0% of patients and 14.0% of control individuals (P <.001). Demodex density was 5.6±4.2 in the PPR group and 0.3±1.0 in the acne group (P <.001). SNS performed well in differentiating between PPR and acne vulgaris, with an area under the receiver operating characteristic curve of 0.89. Diagnosis of PPR per the criterion Demodex density of ≥3 mites per five pustules had a sensitivity of 78% and a specificity of 97%.
In the PPR group, standardized skin surface biopsy yielded positive results for 15 patients (37.5%). No correlation was observed between Demodex density as measured by SNS and that measured by standardized skin surface biopsy (P =.272). However, SNS and standardized skin surface biopsy gave mutually concordant results in half the patients when Demodex density of ≥3 mites per 5 pustules was defined as a positive SNS result.
This study was limited by its small sample size, as well as the inclusion of data from only a single center.
These data suggest that SNS may be a convenient alternative to standardized skin surface biopsy in assessing Demodex density in PPR pustules, and “can be a useful alternative or an addition to” standardized skin surface biopsy. Further study in a larger cohort is necessary to explore the efficacy and accuracy of SNS in capturing Demodex mite densities.
Huang HP, Hsu CK, Lee JY. A new superficial needle-scraping method for assessing Demodex density in papulopustular rosacea [published online July 25, 2019]. J Cosmet Dermatol. doi:10.1111/jocd.13082