Stool test


A stool test involves the collection and analysis of fecal matter to diagnose the presence or absence of a medical condition.

Visual examination

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 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 and the U.S. Preventive Services Task Force recommend screening with either DNA testing every three years, a guaiac fecal occult blood test, or a fecal immunochemical test every year starting at age 45. Other options include a sigmoidoscopy or virtual colonoscopy every five years or a colonoscopy every 10 years. The National Committee for Quality Assurance issued an update to the Healthcare Effectiveness Data and Information Set for 2017, while the guideline remain for the patients aged 50 or over.
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 compared to colonoscopy or fecal occult blood testing. Three-year sDNA screening has been estimated to cost $11,313 per quality-adjusted life year compared with no screening.

Microbiology tests

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 can also be identified. Viruses such as rotavirus can also be found in stools.

Chemical tests

A fecal pH test may be used to determine lactose intolerance or the presence of an infection. Steatorrhea can be diagnosed using a fecal fat test, which checks for the malabsorption of fat.
Faecal elastase levels are becoming the mainstay of pancreatitis diagnosis.