Dermoscopy, light microscopy, and real-time polymerase chain reaction for the diagnosis of scabies. Preliminary results

Introduction: Scabies is a widespread, contagious parasitic disease causing intense itching. Its detection is a significant problem while there are no internationally agreed standards. Aim: To compare diagnostic methods: microscopy of skin scrapings, dermoscopy, and real-time polymerase chain reaction (PCR) of skin scrapings and wet skin swabs. Material and methods: We included patients with clinical signs of scabies. After dermoscopic evaluation, scrapings were collected from skin lesions and assessed by light microscopy and real-time PCR. Wet skin swabs were also analysed by real-time PCR. Surveys on the presence and severity of pruritus and skin lesions were collected. Seventy-five skin scrapings and 41 wet swabs were examined by real-time PCR. Fifty-three patients completed the survey. All patients underwent dermoscopy and microscopy examinations. 6.67% were positive by microscopy, 10.7% by dermoscopy, 28.0% by real-time PCR from scrapings, and 36.6% when both scrapings and swabs were examined by real-time PCR. All microscopy-positive results were also positive by PCR. Results: There was a correlation between real-time PCR from positive scrapings and pruritus (p = 0.023) and body surface area of lesions (p = 0.002), a correlation between copies from wet skin swabs and BSA of lesions (p = 0.002) in the whole group, and a correlation between copies of S. scabiei from scrapings and age (p = 0.038). Conclusions: Real-time PCR testing of scrapings and dermoscopy are more effective than microscopy. Combined real-time PCR testing of scrapings and skin swabs seemed the most effective. Clinical signs alone should not be used as unambiguous criteria.