Does this test have other names?

Giardia antigen (feces)

What is this test?

This is a stool sample test to look for the parasite Giardia intestinalis. The parasite causes an infection of the small bowel called giardiasis. It may also be a cause of travelers' diarrhea. Symptoms include:

• Diarrhea.

• Foul-smelling, fatty stools.

• Bloating, excessive gas (flatus).

• Nausea.

• Vomiting.

• Belly (abdominal) cramps.

• Dehydration.

• Weakness, fatigue.

Giardiasis is common in daycare centers and among people who travel to different countries. It can also be spread through water and food that contain the parasite.

Parasites like Giardia usually have a life cycle in which they pass through several different forms. Because of this, they may not be found right away.

Why do you need this test?

You might need this test if you have unexplained diarrhea or other symptoms listed above, and your doctor thinks that you may have this infection.

What other tests might you have along with this test?

You may also have a white blood cell count test. This is done to check for infection. You may also have other tests to look for other germs in your stool.

What do your test results mean?

Test results may vary depending on your age, sex, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your doctor what your test results mean for you.

If the lab finds the parasite in your stool sample, you likely have giardiasis. But Giardia may not be in the first sample. More than one sample may be needed for an accurate diagnosis.

How is this test done?

This test needs a stool sample. You may be asked to provide more than one sample. Your doctor will tell you how to collect a sample. You will do it with a disposable specimen container with a lid. Don't collect stool from the toilet bowl. Don't put toilet paper into the specimen container or pee into it.

Does this test pose any risks?

This test has no known risks.

What might affect your test results?

Barium, medicine for diarrhea, antacids, and mineral oil can interfere with this test. Antibiotic treatment can also affect the test results.

How do you get ready for this test?

You don't need to prepare for this 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 illegal drugs you may use.