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.

Duodenal parasites test

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.

You may be asked not to eat or drink anything for 12 hours before the test.

You may find it difficult to swallow the string, and you may feel an urge to vomit when the string is being removed.

The test is performed when the doctor suspects a parasite infection, but no parasites were found in a stool sample.

Images

Ascaris lumbricoides egg

Gelatin capsule in stomach

Next Section

String test Results

Review Date: 04/18/2010
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; George F Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)