A stool test involves the collection and analysis of fecal matter to diagnose the presence or absence of a medical condition.
Transport vials filled with human feces for stool testing. Yellow and blue tops for parasite testing, red top for stool cultures and the white top was provided by the patient with the sample.
The patient and/or health care worker in the office or at the bedside is able to make some important observations.
One of the most common stool tests, the fecal occult blood test can be used to diagnose many conditions that cause bleeding in the gastrointestinal system including colorectal cancer or stomach cancer. Cancers, and to a lesser extent, precancerous lesions, shed abnormal cells into the stool.> Cancers and precancerous lesions (polyps) that are ulcerated or rubbed by passing stool also may shed blood into the stool, which can be identified by a hemoglobin assay.
The American Cancer Society recommends screening with either DNA testing every three years, guaiac fecal occult blood test, or fecal immunochemical test every year starting at age 50. Other options include sigmoidoscopy or virtual colonoscopy (CT colonography) every five years or colonoscopy every 10 years.
A DNA test using stool samples was approved in August 2014 by the FDA as a screening test for non-symptomatic, average-risk adults 50 years or older. A 2017 study found this testing to be less cost effective as compared to colonoscopy or fecal occult blood testing. Three-year sDNA screening has been estimated to cost $11,313 per quality adjusted life year (QALY) compared with no screening.
Parasitic diseases such as ascariasis, hookworm, strongyloidiasis and whipworm can be diagnosed by examining stools under a microscope for the presence of worm larvae or eggs. Some bacterial diseases can be detected with a stool culture. Toxins from bacteria such as Clostridium difficile ("C. diff.") can also be identified. Viruses such as rotavirus can also be found in stools.
Faecal elastase levels are becoming the mainstay of pancreatitis diagnosis.
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