For this test, you swallow a gelatin capsule attached to a long string. The end of the string remains outside the mouth and is taped to your cheek. The capsule dissolves in the stomach and the string passes into the upper part of the small intestine (duodenum).
The string is left in place for 4 to 6 hours or overnight. Then it is withdrawn and the end is examined under the microscope for parasites that are attached to it.
This test is also called the Enterotest.
Why It Is Done
The string test may be done if other methods (especially examination of stool samples and antigen tests) have failed to detect giardiasis.
This test is rarely done. If a small sample of the small intestine is needed to confirm the diagnosis, endoscopy is usually done.
Findings of the string test may include the following.
No Giardia parasites are seen when the string is examined.
Giardia parasites can be seen when the string is examined under a microscope.
What To Think About
This test requires you to commit most of a day to the testing procedure. If the string is removed too soon, it may not have had time to reach the small intestine, and the results may be inaccurate. But the test is relatively inexpensive and accurate when done properly.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerW. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Current as ofMay 22, 2015