Demodex Mite Density Determinations by Standardized Skin Surface Biopsy and Direct Microscopic Examination and Their Relations with Clinical Types and Distribution Patterns

BACKGROUND: Demodicosis is a parasitic skin disease caused by Demodex mites, and the determination of mite density per square centimeter is important to diagnose demodicosis. Standardized skin surface biopsy (SSSB) and direct microscopic examination (DME) are commonly used to determine Demodex mites density (Dd). However, no study has previously compared these two methods with respect to clinical types and distribution patterns of demodicosis. OBJECTIVE: The aim of this study was to compare the value of SSSB and DME findings in reference to the clinical types and distribution patterns of demodicosis. METHODS: The medical records of 35 patients diagnosed with demodicosis between December 2011 and June 2015 were retrospectively reviewed. Demodicosis was classified according to four clinical types (pityriasis folliculorum, rosacea type, acne type, and perioral type) and three distribution patterns (diffuse pattern, U-zone pattern, and T-zone pattern). Two samples, one for SSSB and one for DME, were obtained from a lesion of each patient. RESULTS: In all patients, mean Dd and the proportion with a high Dd (>5D/cm²) by DME (14.5±3.3, 80.0%, respectively) were higher than by SSSB (5.5±1.3, 37.1%, respectively; p<0.01, p=0.02, respectively). In terms of clinical types, for rosacea type, mean Dd and proportion with a high Dd by DME (12.4±3.5, 84.6%, respectively) were significantly greater than those determined by SSSB (3.6±1.2, 23.1%; p=0.04, p=0.04, respectively). In terms of distribution pattern, for the diffuse pattern, mean Dd and the proportion with a high Dd by DME (17.5±3.7, 100%, respectively) were significantly higher than those determined by SSSB (6.0±2.7, 26.7%; p<0.01, p<0.01, respectively). CONCLUSION: The results of our study revealed that DME is a more sensitive method for detecting Demodex than SSSB, especially in patients with diffuse pattern and suspected rosacea type. Further research is needed to confirm this finding.

Skin scrapings versus standardized skin surface biopsy to detect Demodex mites in patients with facial erythema of uncertain cause – a comparative study.

Background: Standardized skin surface biopsy (SSSB) is considered to be the gold standard technique to evaluate the density of Demodex mites for the diagnosis of demodicidosis. Potassium hydroxide (KOH) preparation of skin scrapings is a much simpler procedure that can be used to detect pathogens in the superfi cial skin. Objective: To evaluate the reliability of potassium hydroxide preparation of skin scrapings as compared to the standard skin biopsy technique with regard to capacity to detect Demodex mites, time consumed and technician satisfaction. Methods: One hundred outpatients presenting with facial erythema of uncertain cause were enrolled. Standardized skin surface biopsy and potassium hydroxide preparation of skin scrapings were undertaken in adjacent areas on the patients’ right cheek. Limitation: Patients with normal facial skin were excluded from the study. Results: The accuracy of Demodex mite detection by potassium hydroxide preparation of skin-scrapings when compared to the standard procedure is 82%. The sensitivity, specifi city, positive and negative predictive values of this method are 75%, 84.2%, 60% and 91.43%, respectively. There was no statistically signifi cant difference between the standard and skin scraping techniques (P = 0.238) with regard to mite detection. Mean preparation time while using the skin scraping technique was 6 times less than that of the standard technique. For interpretation also, skin scraping technique (3.6 min) consumed much less time than the biopsy technique (9.8 min). Moreover, experienced technicians were more satisfi ed with skin scraping. Conclusion: Potassium hydroxide preparation of skin scrapings is an effective, time saving and practical technique to detect Demodex mites with accuracy comparable to the standard biopsy method.