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 superficial 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, specificity, positive and negative predictive values of this method are 75%, 84.2%, 60% and 91.43%, respectively. There was no statistically significant 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 satisfied 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.