Slit smears - leprosy
Slit skin smears are used for the determination of the number of bacilli and the state of those bacilli, in the lesions of patients undergoing treatment for leprosy.
The lesion is first cleaned with alcohol. The skin is pinched to make it bloodless. An incision is made into the crest of the pinched skin with a scalpel blade (#15), 5 mm long to a depth of 3 mm. The blade is then turned 90 degrees and the tissue is scraped repeatedly in one direction. The scrapings are gently spread onto a glass slide, the slide is fixed, and is stained for acid-fast bacilli.
Acid-fast bacilli are common in lepromatous leprosy; they are absent or rare in tuberculoid. With adequate treatment, lepromatous smears become negative in a few years (up to 10).
Slit smears of lesions are superior to a nasal scraping in the assessment of response to therapy. Nasal scrapings become negative sooner than slit skin smears.