- The most common way to diagnose giardiasis is by the visualization of the
Giardia cysts by experienced laboratory professionals. The cysts are detected 50%
to 70% of the time in the first stool specimen examined. Over 90% of the time the cysts are detected after
three stool specimens have been examined. So more than one specimen may be required.
- Another method of diagnosis that is commonly used as a screening tool in outbreaks or in daycare centers is antigen assay of stool. This method detects a certain protein found in the wall of
Giardia. A stool sample is mixed with a solution that detects the cysts in the stool.
- The string test involves swallowing a fuzzy string enclosed in a gelatin capsule. The free end of the string is taped to the person's cheek. Once swallowed, the string collects secretions and mucus from the small bowel. Four hours later the string is pulled back out and examined for organisms.
Aspiration and biopsy
- This is the most invasive method of diagnosis. After passage of a small telescope through the person's mouth and stomach into the small bowel, the doctor removes a small amount of tissue for examination. This method is reserved for difficult cases in which the cause of diarrhea cannot be determined using other methods. It allows for visualization of all abnormalities of the small intestine, which may cause diarrhea including giardiasis.
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