Efficacy and safety of a lindane 1% treatment regimen for scabies, confirmed by dermoscopy-guided skin scraping with microscopic examination

Background This is the first study investigating scabies treatment since 1992 to involve examination of patients with microscopically confirmed scabies. Aim To assess the efficacy of 1% lindane cream in treating microscopically confirmed scabies, and to determine the utility of dermoscopy-guided skin scraping with microscopic examination (DSGSS-ME) in evaluating the efficacy of scabies treatment. Methods This retrospective study analysed patients treated for scabies between January 2012 and December 2013. From the hospital database, 287 cases of scabies were identified and 50 were enrolled in the study. Patients were treated with 1% lindane cream twice weekly (days 0 and 1) and were evaluated with DSGSS-ME on day 7. Treatment and evaluations were repeated once weekly until a negative DSGSS-ME result was obtained. Results The cumulative efficacy of lindane 1% cream was 40% (20/50) after 1week, 88% (44/50) after 2weeks and 98% (49/50) after 3weeks of treatment. There was a statistically significant difference between the 1- and 2-week (P=0.03), and 1- and 3-week (P=0.02) treatments. A total of 90 post-treatment DSGSS-MEs were performed, with a sensitivity of 97.3% (95% CI 85.8-99.9) and a negative predictive value of 98.2% (95% CI 90.1-100). Specificity and positive predictive value were 100%, as this procedure cannot yield false-positive results, because it relies on finding mites, eggs or faeces. Conclusions We suggest that a twice-weekly schedule (on consecutive days) of 1% lindane treatment lasting at least 2weeks is required to clear scabies. DSGSS-ME appears to be a good method to evaluate the efficacy of scabies treatment. This study introduces a safe and effective method to treat scabies, and to accurately monitor infestation status in patients.