Coordinated Health



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 detect the presence of intestinal parasites. The string test is rarely used in the United States.

Alternative Names

Duodenal parasites test

How the test is performed

You swallow a string with a weighted gelatin capsule on the end. Four hours later it is pulled back out. Any bile, blood, or mucus attached to the string is examined under the microscope 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 difficult to swallow the string, and you may feel 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, but no parasites were found in a stool sample.

Normal Values

No blood, parasites, fungi, or abnormal cells is normal.

Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.

What abnormal results mean

Abnormal results may be a sign of giardia or another parasite infection.

Special considerations

Treatment with certain drugs can affect the test results.