26. Garcia LS, Brewer TC, Bruckner DA. 1979. A comparison of the formalin-ether concentration and trichrome-stained smear methods for the recovery and identification of intestinal protozoa. Am J Med Technol 45:932–935. PMID 92195
27. Dunn FL. 1968. The TIF direct smear as an epidemiological tool, with special reference to counting helminth eggs. Bull WHO 39:439–449. PMID 5303910
28. Brooke MM, Goldman M. 1949. Polyvinyl alcohol-fixative as a preservative and adhesive for protozoa in dysenteric stools and other liquid material. J Lab Clin Med 34:1554–1560.
29. Garcia LS, Shimizu RY, Brewer TC, Bruckner DA. 1983. Evaluation of intestinal parasite morphology in polyvinyl alcohol preservative: comparison of copper sulfate and mercuric chloride base for use in Schaudinn’s fixative. J Clin Microbiol 17:1092–1095. PMID 6223937
30. Horen WP. 1981. Modification of Schaudinn fixative. J Clin Microbiol 13:204–205. PMID 7462413
31. Garcia LS, Shimizu RY, Shum A, Bruckner DA. 1993. Evaluation of intestinal protozoan morphology in polyvinyl alcohol preservative: comparison of zinc sulfate- and mercuric chloride-based compounds for use in Schaudinn’s fixative. J Clin Microbiol 31:307–310. PMID 7679402
32. Garcia LS (ed). 2010. Clinical Microbiology Procedures Handbook, 3rd ed. ASM Press, Washington, DC.
33. International Air Transport Association (IATA). 2013. Dangerous Goods Regulations, 54th Ed., Montreal, Canada. http://www.iata.org/publications/dgr/Pages/manuals.aspx (accessed 4/17/13)
34. Gray LD, Snyder JW. ASM Laboratory Protocol Working Group. 2011. Sentinel Laboratory Guidelines for Suspected Agents of Bioterrorism and Emerging Infectious Diseases: Packing and Shipping Infectious Substances. American Society for Microbiology, Washington, DC. http://www.asm.org/images/pdf/Clinical/pack-ship-7-15-2011.pdf (accessed 3/12/15).
35. Kehl KSC. 1996. Screening Stools for Giardia and Cryptosporidium: are antigen tests enough? Clin Microbiol Newsl 18:133–135.
36. Morris AJ, Wilson ML, Reller LB. 1992. Application of rejection criteria for stool ovum and parasite examinations. J Clin Microbiol 30:3213–3216. PMID 1452704
37. Siegel DL, Edelstein PH, Nachamkin I. 1990. Inappropriate testing for diarrheal diseases in the hospital. JAMA 263:979–982. PMID 2299766
If the consistency of a stool specimen can be determined (formed, soft, or liquid), this information may give an indication of the organism stages that might be present. Trophozoites (potentially motile forms) of the intestinal protozoa are usually found in liquid specimens; both trophozoites and cysts might be found in a soft specimen; and the cyst forms are usually found in formed specimens. However, there are always exceptions to these general statements. Coccidian oocysts and microsporidian spores can be found in any type of fecal specimen; in the case of Cryptosporidium spp., the more liquid the stool, the more oocysts that are found in the specimen. Helminth eggs may be found in any type of specimen, although the chances of finding eggs in a liquid stool are reduced by the dilution factor. Tapeworm proglottids may be found on or beneath the stool on the bottom of the collection container. Adult pinworms and Ascaris lumbricoides are occasionally found on the surface or in the stool.
The presence of blood in or on the specimen may indicate several things and should always be reported. Dark stools may indicate bleeding high in the gastrointestinal tract, and fresh (bright red) blood most often is the result of bleeding at a lower level. In certain parasitic infections, blood and mucus may be present. Soft or liquid stool accompanied by blood is more suggestive of an amebic infection; these areas of blood and mucus should be carefully examined for the presence of trophic amebae. Occult blood in the stool may or may not be related to a parasitic infection and could result from a number of different conditions. Ingestion of various compounds may give a distinctive color to the stool (iron, black; barium, light tan to white).
Many laboratories prefer that stool specimens be submitted in some type of preservative. Rapid fixation of the specimen immediately after passage (by the patient) provides an advantage in terms of recovery and identification of intestinal protozoa. This advantage (preservation of organisms before distortion or disintegration) is thought to outweigh the limited motility information that might be gained by examining fresh specimens as direct wet mounts. Other laboratories still
