Comparison of two techniques for measuring Demodex folliculorum and Demodex brevis in rosacea patients: standardized skin surface biopsy vs. direct microscopic examination.

Rosacea is a chronic inflammatory skin disease affecting approximately 5.4% of the world population. Among its pathogenic factors is infestation by Demodex spp. Standardized skin surface biopsy (SSSB) and direct microscopic examination (DME) are widely used methods to measure Demodex spp density (Dd); however, there is no agreement on the method of choice, nor the prevalence of infestation in rosacea patients. This study compared both techniques in rosacea patients. A prospective study was conducted with 61 patients diagnosed with rosacea by dermatologists from two dermatology centres. Dd was evaluated using SSSB and DME in each patient. Results, median sampling time and reported pain were analyzed using appropriate statistical methods. The median Dd was significantly higher with SSSB (11 mites/cm²) compared to DME (1 mites/cm²; P < 0.001). Infestation (>5 mites/cm²) was detected in 64% of patients with SSSB and in 28% with DME (P < 0.001). The median sampling time was longer for SSSB (60 s) than for DME (30 s; P < 0.001). Both methods were associated with mild pain, slightly lower with DME (P = 0.033). SSSB proved more effective than DME for detecting Demodex spp. in rosacea, identifying a greater total number of mites and a higher percentage of infestation. Up to 64% of rosacea patients showed infestation with Demodex spp. using the SSSB technique. The results reinforce the use of SSSB as the standard technique for diagnosing Demodex spp. infestation in rosacea patients.