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String test

  • Definition
    • 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.

  • Alternative Names
    • Duodenal parasites test; Giardia - string 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. This is done 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. Usually a stool sample is tested first. A string test is done if the stool sample is negative.

  • Normal Results
    • 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.

  • What Abnormal Results Mean
    • Abnormal results may be a sign parasite infection such as giardia.

  • Considerations
    • Treatment with certain drugs can affect the test results.

  • References
    • Beavis, KG, Charnot-Katsikas, A. Specimen collection and handling for diagnosis of infectious diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. Philadelphia, PA: Elsevier; 2017:chap 64.

      Bope ET, Kellerman RD. The infectious diseases. In: Bope ET, ed. Conn's Current Therapy 2016. Philadelphia, PA: Elsevier; 2016:chap 3.

      Haines CF, Sears CL. Infectious enteritis and proctocolitis. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 110.

      Hall GS, Woods GL. Medical bacteriology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. Philadelphia, PA: Elsevier; 2017:chap 58.

      Hill DR, Nash TE. Giardia lamblia. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 281

      Siddiqi HA, Salwen MJ, Shaikh MF. Laboratory diagnosis of gastrintestinal and pancreatic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. Philadelphia, PA: Elsevier; 2017:chap 22.