- Ova & Parasites (Stool)
- O&P (Stool)
- Parasites and ova stool exam
- Parasitology examination
- Stool O&P
Stool (feces) specimen
- Blue top vial/container or sterile, tightly capped container (provided by lab) OR container with preservative [10% formalin and/or polyvinyl alcohol (PVA) fixative]
- Submit 10-20 g (2-5 mL) of stool
Additional information
- Stool collection:
- Clear instructions should be communicated and given in writing to the patient to ensure proper collection
- Instruct the patient to defecate in a large-mouthed plastic container, bag, or clean bedpan
- If the patient has diarrhea, a large plastic bag can be attached by adhesive tape to the toilet seat
- Wearing gloves, collect the entire stool specimen and transfer it to a container using a clean tongue blade or similar object
- Provide for and respect the person's privacy
- Stool can be collected from the diaper of an infant or incontinent adult. Samples can be collected from temporary ostomy bags
- 3 separate random stool specimens collected every other day, preferably within 10 days may be required (up to 6 specimens required for E. histolytica)
- Empty bladder completely; avoid contamination with water, urine or other body secretions such as menstrual blood
- Stop the use of any laxative, barium sulfate, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapy2 weeks prior to the test
- Label the samples properly, including the date and time of the collection of stool
- Record recent dietary and travel history if patient has diarrhea
- Send the specimen to lab immediately and do not refrigerate
- Stool Ova & Parasites testing is a microscopic examination of the stool to detect the presence of ova (eggs, cyst forms) and parasites in a stool sample
- A wide variety of intestinal parasites (worms, eggs, protzoa) can be detected by stool examination
- 1/3rd are protozoa, and 2/3rd are multicellular worms
- 6 types of intestinal protozoa are clinically important
- Almost all of the intestinal worms (helminths) are potentially pathogenic
- Submission of adequate number of specimens is essential as false negative results occur frequently
False negative rates:
- 1 specimen: 25-33%
- 2 specimens: 8-15%
- 3 specimens: <10%
Findings may include:
- Protozoa:
- Blastocystis hominis (Blastocystosis)
- Cryptosporidium parvum (Cryptosporidiosis)
- Entameba histolytica (Amebic dysentery/liver abscesses)
- Giardia lamblia (Giardiasis)
- Isospora belli (Isosporiasis)
- Sarcocystis hominis or Sarcocystis suihominis (Sarcocystosis)
- Worms (Helminths):
- Ascaris lumbricoides (Ascariasis)
- Echinococcus granulosus (Echinococcosis)
- Hookworms (Ancylostoma duodenale, Necator americanus)
- Paragonimus westermani (Paragonimiasis)
- Pinworms (Enterobius vermicularis)
- Schistosomiasis (Schistosoma mansoni, Schistosoma japonicum, Schistosoma hematobium)
- Strongyloides stercoralis (Strongyloidiasis)
- Tapeworms (Taenia saginatus, Taenia solium, Diphyllobothrium, Hymenolepis nana, Hymenolepis diminuta)
- Trematodes (Fasciola hepatica, Clonorchis sinensis, Fasciolopsis buski)
- Whipworms (Trichuris trichiura)
- The clinical utility of stool ova and parasite testing includes:
- Evaluation of persons presenting with symptoms and signs of gastrointestinal parasitic infection
- To detect parasitic diseases in symptomatic persons at risk of intestinal infestation, such as:
- Immunocompromised persons
- AIDS
- Debilitated elderly persons
- Recently traveled outside the US
- Consumption of water from stream or lake while camping
- Close contact with infected persons
- Children
- To monitor response to pharmacology therapy for parasitic diseases
- Intestinal parasitic infections are transmitted most often by fecal-oral route or direct penetration through the skin from contaminated soil or animal droppings. The sources of infection include:
- Community acquired, from intermediate hosts such as dogs and other pets, through intake of contaminated water
- Occupational
- Fishermen, from snails and worms
- Meat cutters, from contaminated animals
- Healthcare workers, from patients
- Farm workers, from animals (cows, pigs), garden, flies, mosquitoes, insects, fleas, bugs, etc
- Recreational
- Backpacking, poor sanitation
- Traveling to places with contaminated water supply
- Contact with fair animals
- From contaminated soil or in animal droppings by direct penetration of the skin (larva of hookworm infection)
- Nosocomial infection
- Personal contact with an infected host
- Parasitic infections most often clinically present with:
- Abdominal pain or cramping
- Diarrhea (Prolonged, may be bloody or have mucous)
- Mucous in stool
- Nausea
- Systemic symptoms (Fever, Headache)
- With helminth infections (Worms noted in stool, Perianal itching)
- Certain parasites may migrate from the intestine to other parts of the body, for example, Ascaris lumbricoides may perforate bowel wall causing peritonitis, or may migrate to lungs causing pneumonia
- Hookworms can cause hypochromic microcytic anemia especially in persons with iron deficient diets
- The Tapeworm D. latum may cause megaloblastic anemia by depleting vitamin B12
Additional information
- The most common parasites in the U.S. are Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum, Enterobius vermicularis, Ancylostoma duodenale, and Necator americanus
- Factors interfering with the test results include:
- Persons receiving laxatives, barium, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapywithin 2 weeks prior to the stool collection
- Specimen not transported promptly (trophozites in liquid stool disintegrate rapidly after defecation)
- Improper collection technique or collection of too few specimens
- Exposure of specimen to excessive heat or cold
- Stool specimen contaminated with urine or water can destroy trophozoites
- Stool collected from toilet bowl may contain other organisms
- Additional tests may be required in certain disease conditions as the extent of infection may depend on the degree of tissue invasion by the parasite, such as
- If amebiasis is suspected but stool exams are negative, specimen collection after saline cathartic using buffered sodium biphosphate or during sigmoidoscopy may be essential
- If giardiasis or S. stercoralis is suspected but stool exams are negative, examination of duodenal contents may be essential
- Related laboratory tests include
- Antigen testing
- Biopsy of liver
- Casoni's skin test
- Complete blood count (Eosinophils may be elevated)
- Scotch tape test for Enterobius vermicularis
A normal result is:
- No presence of parasites, ova, or larvae
Method:
- Concentration of stool material and examination by iodine/saline and trichrome staining
A positive result indicates the possibility of intestinal parasite infection. Additional testing may be required for confirmation (false positives occur).
- Submission of adequate number of specimens is essential as false negative results occur frequently
- False negative rates:
- 1 specimen: 25-33%
- 2 specimens: 8-15%
- 3 specimens: <10%
- Factors causing false negative test results include:
- Antimicrobial or antiamebic therapy within 10 days of test
- Contamination of sample with urine
- Failure to test a fresh specimen
- Sample is not representative of the entire stool evacuation
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