Synonym

• Ova & Parasites (Stool)
• O&P (Stool)
• Parasites and ova stool exam
• Parasitology examination
• Stool O&P

Tubes

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

Info

• 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
• 1/3^rd are protozoa, and 2/3^rd 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)

Clinical

• 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

Nl Result

A normal result is:

• No presence of parasites, ova, or larvae

Method:

• Concentration of stool material and examination by iodine/saline and trichrome staining

High Result

A positive result indicates the possibility of intestinal parasite infection. Additional testing may be required for confirmation (false positives occur).

Low Result

• 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

References

• ARUP Laboratories®. Ova & Parasite Exam, Fecal. [Homepage on the internet]©2007. Last accessed on March 2, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0060240.jsp
• Cartwright, C.P. Utility of Multiple-Stool-Specimen Ova and Parasite Examinations in a High-Prevalence Setting. J Clin Microbiol. 1999 August; 37(8): 2408-2411.
• Centers for Disease Control: Collection and Preservation of Fecal Laboratory Specimens. [Homepage on the Internet]. Last accessed on March 2, 2007. Available at URL: http://www.dpd.cdc.gov/DPDx/CEUs/Lab_tech_ceu.asp?body=Lab_Tech/body_labtech_directions.htm
• eMedicine from WebMD®. Intestinal Protozoal Diseases. [Homepage on the Internet] ©1996-2006. Last updated on October 4, 2006. Last accessed on March 1, 2007. Available at URL: http://www.emedicine.com/ped/topic1914.htm
• Kucik,C.J., Martin,G.L., Sortor,B.V. Common intestinal parasites. Am Fam Physician. 2004;69(5):1161-1168. Available at URL: http://www.aafp.org/afp/20040301/1161.html
• Laboratory Corporation of America. Ova and Parasites Examination. [Homepage on the internet]©2007. Last accessed on March 2, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb010500.htm
• LabTestsOnline®. O&P. [Homepage on the Internet]© 2001-2006. Last reviewed onDecember 27, 2004. Last accessed on March 2, 2007. Available at URL: http://www.labtestsonline.org/understanding/analytes/op/glance.html
• Tinuade O et al. Parasitic etiology of childhood diarrhea. Indian J Pediatr. 2006 Dec;73(12):1081-4.
• Wiwanitkit V et al. Intestinal parasite infestation in HIV infected patients. Curr HIV Res. 2006 Jan;4(1):87-96.