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Ova and Parasites Stool Test

Last updated July 23, 2019

Approved by: Maulik P. Purohit MD MPH

The Ova and Parasites Stool Test (O & P Test) is used to detect the presence of specific parasites within the human digestive tract.


What are the other Names for this Test? (Equivalent Terms)

  • Ova and Parasites Exam
  • Parasitic Examination Stool Test
  • O & P Test 

What is Ova and Parasites Stool Test? (Background Information)

  • Parasites are single- or multi-celled organisms that infect many parts of the body, including the intestinal tract. They originate from ova, or eggs, that are resistant to the harsh conditions they may encounter inside a host, or while changing hosts
  • Virtually, all single-celled parasites fall within the protist kingdom. They consist of:
    • Amoebas, such as E. histolytica (causing dysentery, liver abscesses) and N. fowleri (causing encephalitis)
    • Flagellates, such as G. intestinalis (causing diarrhea), T. vaginalis (causing vaginitis)
    • Apicomplexa, such as C. parvum (causing diarrhea), T. gondii (causing flu-like illness), and P. falciparum (causing malaria)
  • Multi-celled parasites are called helminths, or worms. They include:
    • Cestodes, such as Taenia (commonly known as tapeworms)
    • Trematodes, such as Schismosoma (commonly known as flukes)
    • Nematodes, such as Enterobius (commonly known as pinworm), Necator (known as hookworms), and Strongyloides (known as roundworm)
  • Parasites vary in their potential to cause diseases and the severity of the diseases that they may cause. Symptoms may be non-existent, mild, or severe, depending on the type of parasite
  • Parasites that affect the gastrointestinal tract are usually ingested by the host, through contaminated food and water. Other parasites, such as the protozoan responsible for malaria, are spread through insect carriers, or vectors
  • Eggs, or ova, of parasites are often very resilient. This allows them to survive the adverse conditions of a host’s gastrointestinal tract or whatever medium the parasites use, to spread the eggs to other hosts
  • The Ova and Parasites Stool Test (O & P Test) is used to detect the presence of specific parasites within the human digestive tract

What are the Clinical Indications for performing the Ova and Parasites Stool Test?

Following are the clinical indications for performing an Ova and Parasites Stool Test:

  • Prolonged diarrhea or bloody diarrhea
  • Abdominal pain
  • Nausea or vomiting
  • Iron deficiency anemia
  • Weight loss 

How is the Specimen Collected for Ova and Parasites Stool Test?

Following is the specimen collection process for Ova and Parasites Stool Test:

Sample required: Stool

Process: Collection of a sample of feces using a sterile container.

Preparation required: No special preparation is needed prior to the test. 

What is the Significance of the Ova and Parasites Stool Test Result?

  • A positive result from an Ova and Parasites Stool Test may indicate infection by one or more parasites

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario. 

Additional and Relevant Useful Information:

  • Individuals with compromised immune systems are particularly susceptible to parasitic infections
  • The most common parasites in the US are Giardia, Cryptosporidium, and E. histolytica. They are especially prevalent in warm areas, in regions that lack proper water treatment 

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 2, 2014
Last updated: July 23, 2019