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Microscopic examination of sputum is used in identifying Paragonimus westermani eggs, Strongyloides stercoralis larvae, Ascaris lumbricoides larvae, hookworm larvae, and rarely Entamoeba histolytica. Sputum should be obtained from the lower respiratory passages rather than a sample consisting mainly of saliva. Sputum specimens should be collected first thing in the morning. A sputum sample can be examined in several ways:
- The unfixed specimen may be centrifuged and then the sediment examined as a direct wet mount.
- If the sputum is too viscous, an equal volume of 3% sodium hydroxide may be added, then centrifuge, and examine the sediment.
- The specimen may be preserved in 10% formalin and a formalin-ethyl acetate concentration procedure may be completed and the sediment examined using either a wet mount or a stained preparation.
- The specimen may also be preserved in PVA if protozoa are suspected and stained with trichrome stain.
For additional information about sputum specimens, call the Division of Parasitic Diseases, at (404) 718-4110.