Manual of basic techniques for a health laboratory - libdoc.who.int

222 Manual of basic techniques for a health laboratoryappears to be altering most rapidly. (This is important, to ensure thatbacilli are detected.)A sample can also be taken from an area of skin showing the first signs ofleprous infiltration.2. Disinfect the area using a gauze swab soaked in ethanol. Flame the clampforceps and scalpel.3. Squeeze the site hard using the forceps and make an incision about 0.5cmlong and 2–3mm deep with the tip of the scalpel (Fig. 5.42).4. Still squeezing with the forceps, scrape the bottom and edges of the incisionwith the tip of the scalpel. Collect a small amount of pulp and serousmaterial. Disinfect the incision with ethanol and apply a dressing if thereis bleeding.Fig. 5.40 Leprosy lesions on the armSpecimens from the noseSpecimens are best prepared from an early morning “nose blow”. The patientblows his or her nose thoroughly into a small clean dry sheet of cellophaneor plastic.Preparation of slidesSpecimens from the ear and skin lesions1. Spread the serous material from the tip of the blade on to the slide in a circularmotion until it covers an area of 5–7mm in diameter (Fig. 5.43). Label the slidewith a diamond pencil. Between two and four smears from the same patientmay be prepared on a single slide.2. Leave the slide to dry in a dust-free place and then fix the smears by passing theback of the slide through the flame of a spirit lamp or Bunsen burner severaltimes.3. Stain the smears using the modified Ziehl–Neelsen technique (see section 5.3.3).Specimens from the body and face1. Using the scalpel, spread the specimen in a circular motion over an area 5–7mm in diameter on a glass slide labelled with a diamond pencil. Betweenthree and six specimens from the same patient can be placed on the same slide.2. Dry and fix the smears as for specimens from the ear or skin lesions (see above).3. Stain the smears using the modified Ziehl–Neelsen technique (see section 5.3.3).Fig. 5.41 Leprosy lesions on thefaceFig. 5.42 Collecting a specimen from a skin lesion