Giardia Lamblia (cont.)
How is giardiasis diagnosed?
The best single test for diagnosing giardiasis is antigen testing of the stool. For
antigen testing, a small sample of stool is tested for the presence of Giardial
proteins. The antigen test will identify more than 90% of people infected with
Giardia. Giardia also can be diagnosed by examination of stool under the
microscope; however, it takes three samples of stool to diagnose 90%
of cases. Despite requiring three samples of stool, microscopical examination of
stool identifies other parasites in addition to Giardia that can cause diarrheal
illness. Therefore, microscopical examination of stool has value beyond
diagnosing giardiasis, for example, it can diagnose other parasites as the cause of a patient's illness.
Other tests that can be used for diagnosing giardiasis are collection and
examination of fluid from the duodenum or biopsy of the small intestine, but
these require a good deal of discomfort. The string test is a more comfortable
method for obtaining a sample of duodenal fluid. For the string test, a gelatin
capsule that contains a loosely-woven string is swallowed. One end of the string
protrudes from the capsule and is taped to the patients outer cheek. Over
several hours, the gelatin capsule dissolves in the stomach, and the string
uncoils, with the last 12 inches or so passing into the duodenum. In the
duodenum the string absorbs a small amount of duodenal fluid. The string then is
untapped from the cheek and is removed. The collected duodenal fluid is
expressed from the string and is examined under the microscope. Although more
comfortable than some of the other tests, it is not clear how sensitive the
string test is, for example, does it diagnose 60% (not very good) or 90% (very good) of
cases of giardiasis.
Next: How is giardiasis treated? »
- metronidazole, Flagyl - Explains the medication metronidazole (Flagyl) an antibiotic drug used against anaerobic bacterteria and certain parasites like giardia and ameba that can infect parts of the human body. Article includes descriptions, uses, drug interactions, and side effects.
- Endoscopy (Esophagogastroduodenoscopy, EGD) - Learn about the endoscopy procedure which examines the esophagus, stomach and duodenum to detect gastrointestinal and digestive disorders on MedicineNet.com
- Diarrhea - Read the causes of diarrhea including infections, parasites, food poisoning, medications, IBS, IBD, cancer, endocrine disease, fat malabsorption, laxative abuse and more.
Latest Medical News
Digestion RSS