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String test

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. The string test is rarely used in the United States.

Alternative Names

Duodenal parasites test

How the Test is Performed

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 to look 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 hard to swallow the string. You may have 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 Results

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.

Considerations

Treatment with certain drugs can affect the test results.

References

DuPont HL. Approach to the patient with suspected enteric infection. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 291.

Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 142.

Giannella RA. Infectious enteritis and proctocolitis and bacterial food poisoning. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, PA: Saunders Elsevier; 2010:chap 107.

Croft AC, Woods GL. Specimen collection and handling for diagnosis of infectious diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 63.

Salwen MJ, Siddiqi HA, Gress FG, Bowne WB. Laboratory diagnosis of gastrintestinal and pancreatic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 22.

Fritsche TR, Selvarangan R. Medical parasitology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 62.

Updated: 5/15/2014

Jenifer K. Lehrer, MD, Department of Gastroenterology, Frankford-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.


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