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Ova and Parasites (Stool)

Does this test have other names?

Stool sample examination, stool O&P, fecal smear

What is this test?

This test looks for parasites and their larvae or eggs in a sample of your stool.

Parasites are organisms that can live within or on the human body and rely on it as a source of food. Many live in the digestive tract.

Many parasites also cause illnesses. These include one-celled organisms, such as Giardia, and larger organisms such as pinworms. In their adult form, pinworms can usually large enough to be seen.

Why do I need this test?

You may need this test if your doctor suspects that you have parasites in your digestive tract. Giardia and cryptosporidium are common parasitic illnesses. Symptoms include:

  • Stomach upset or bloating

  • Diarrhea

  • Gas

  • Stomach cramping

  • Dehydration

  • Weight loss

Pinworms can live in the colon and rectum. Anal itching is a symptom of a pinworm infection. The itching is usually worse at night and may disturb your sleep.

What other tests might I have along with this test?

Your doctor may also order blood tests and other tests for specific parasites. For example, if your doctor suspects a pinworm infection, you may have to do a "tape test." In this test, the adhesive side of a piece of cellophane tape is gently pressed to the skin around the anus. Pinworm eggs will stick to the tape. Then the eggs can be transferred to a slide and examined under a microscope.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning that no parasites, larvae, or eggs were found in your sample.

Positive results mean that you have an infection with a parasite.

How is this test done?

This test requires a stool sample. Your doctor will tell you how to collect the sample. Don't collect fecal material from the toilet bowl or put toilet paper into the specimen container.

What might affect my test results?

Certain medications can affect your results. This can be true for up to one week after the medications are taken. These medications include:

  • Antacids

  • Bismuth

  • Some drugs used to treat diarrhea

  • Barium

  • Antibiotics

  • Oily laxatives

A sample contaminated by urine or toilet water may have an inaccurate result. Timing is also important. If the sample isn't brought to the lab promptly, the results may not be accurate.

How do I get ready for this test?

You may need to stop taking certain medications before the test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.