String testDuodenal parasites test; Giardia - string test
A string test involves swallowing a string to obtain a sample from the upper part of the small intestine. The sample is then tested to look for intestinal parasites.
How the Test is Performed
To have this test, you swallow a string with a weighted gelatin capsule on the end. The string is pulled out 4 hours later. Any bile, blood, or mucus attached to the string is examined under the microscope. This is done to look for cells and parasites or parasite eggs.
How to Prepare for the Test
You may be asked not to eat or drink anything for 12 hours before the test.
How the Test will Feel
You may find it hard to swallow the string. You may have an urge to vomit when the string is being removed.
Why the Test is Performed
The test is performed when your health care provider suspects that you have a parasite infection. Usually a stool sample is tested first. A string test may be done if the stool sample is negative but a parasite infection is still suspected.
No blood, parasites, fungi, or abnormal cells is normal.
Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your test results.
What Abnormal Results Mean
Abnormal results may be a sign of parasite infection, such as giardia.
Treatment with certain drugs can affect the test results.
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Ascaris lumbricoides egg - illustration
Ascaris lumbricoides egg
Gelatin capsule in stomach - illustration
Gelatin capsule in stomach
Review Date: 5/6/2022
Reviewed By: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.