Qualities of a good sputum smear

Good quality smears are essential for accurate examination and results. A good quality sputum smear is one that is of uniform thickness and made from the mucopurulent portion of the sample in the center of the slide (Figure 1).

Do’s and Don’ts of a Good Quality Smear

• Do ensure that the smear size is 3 cm by 2 cm
• Do ensure there are no fingerprints on the prepared smear

Figure 1: Uniform spread of smear, not too thick or thin, and covering an area of 3cm by 2cm

• The smear should not be very thick, but it should be thin enough to visualize a newsprint as can be seen in Figure 2

Figure 2: Smear thin enough to visualise a print through it

• All smears should be air-dried for 30 minutes, before heat fixing to ensure that the smear is not washed off during staining

Common Mistakes to Be Avoided

Resources

• The Handbook - Laboratory Diagnosis of Tuberculosis by Sputum Microscopy, 2013
• Module for Laboratory Technicians – RNTCP, 2005
• Manual for Sputum Smear Fluorescence Microscopy- RNTCP

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