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is withdrawn and the end is examined under the microscope for parasites that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
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.