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.
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.
You may be asked not to eat or drink anything for 12 hours before the test.
You may find it hard to swallow the string. You may have an urge to vomit when the string is being removed.
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 is done if the stool sample is negative.
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.
Abnormal results may be a sign parasite infection such as giardia.
Treatment with certain drugs can affect the test results.
Reviewed By: Michael M. Phillips, MD, Clinical Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.