Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Diarrhea, malnutrition, anemia, and intestinal obstruction are some of the consequences of infection with intestinal parasites. Protozoa may cause diarrhea and/or malabsorption by elaborating toxins or by adhering to or invading the mucosa or by unknown mechanisms. Cryptosporidiosis occurs as a self-limited moderate diarrhea in young children, especially daycare attendees and their relatives.
Helminths (worms) may obstruct the intestine, cause blood loss, or interfere with the absorption of essential nutrients. Larvae or eggs may disseminate beyond the intestine and cause tissue destruction and provoke inflammation.
Parasitic protozoa and helminths of various types also may inhabit the intestinal tracts of humans and animals without causing disease.
Detection and identification of parasites: included are Giardia, Entamoeba histolytica (amoeba), helminth eggs, protozoa, larval worms, and segments (proglottids) of tapeworms.
See Parasitic Investigation of Stool Specimens Algorithm in Special Instructions for other diagnostic tests that may be of value in evaluating patients with diarrhea.
A positive result indicates the presence of the parasite but does not necessarily indicate that it is the cause of any symptoms. Some strains of protozoa are nonpathogenic and some helminths cause little or no illness.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Stool specimens is suspected of containing tapeworm segments or other adult worms: the suspected worm should be placed in 70% alcohol and submitted as test PARID/9202 Parasite Identification
For optimal results, a specific request should be made for the detection of Cryptosporidium, microsporidium, Cyclospora, or pinworm.
If cryptosporidiosis is suspected, CRYPS/80335 Cryptosporidium Antigen, Feces should be ordered.
This test is not appropriate for the detection of Acanthamoeba, filaria, malaria, trypanosomes, Toxoplasma, or Trichomonas, since these organisms do not occur in the stool.
Examination of a minimum of 3 specimens is required for the detection of > or =90% of some protozoal infections, especially giardiasis.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
If positive, organism identified
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Garcia L, Bruckner D: Diagnostic Medical Parasitology. 3rd edition. Washington, DC, ASM Press, 1997