A stool test is a medical diagnostic technique that involves the collection and analysis of fecal matter. Microbial analysis (culturing), microscopy and chemical tests are among the tests performed on stool samples.

Collection

Stool samples should be sent to the laboratory as soon as possible after collection and should not be refrigerated prior to receipt by the laboratory.

Visual examination

The patient and/or health care worker in the office or at the bedside is able to make some important observations. * Color * Texture/consistency—formed * Classify type of feces (diagnostic triad for irritable bowel syndrome) based on

Bristol stool scale The Bristol stool scale is a diagnostic medical tool designed to classify the form of human faeces into seven categories. It is used in both clinical and experimental fields. It was developed at the Bristol Royal Infirmary as a clinical as ...

Cancer screening

Fecal occult blood test and fecal immunochemical test are the most common stool tests to diagnose many conditions that caused by bleeding in the

gastrointestinal system The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

, including colorectal cancer or

stomach cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the Gastric mucosa, lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenoca ...

. Cancers, and to a lesser extent, precancerous lesions, shed abnormal cells into the stool. Cancers and precancerous lesions (

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) end ...

) 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 The American Cancer Society (ACS) is a nationwide voluntary health organization dedicated to eliminating cancer. Established in 1913, the society is organized into six geographical regions of both medical and lay volunteers operating in more tha ...

and the U.S. Preventive Services Task Force recommended colorectal cancer screening with a fecal immunochemical test every year, or a multi-target stool DNA test for every three years from the age of 45. Other options include a

sigmoidoscopy Sigmoidoscopy (from the Greek term for letter " s/ς" + "eidos" + "scopy": namely, to look inside an "s"/"ς"-like object) is the minimally invasive medical examination of the large intestine from the rectum through to the nearest part of the col ...

or virtual colonoscopy (CT colonography) for every five years or a

colonoscopy Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis ( ...

for every 10 years. Fecal occult blood test is no longer recommended due to the high false-positive rate as well as the dietary and pharmaceutical restrictions. The

National Committee for Quality Assurance The National Committee for Quality Assurance (NCQA) is an independent 501(c)(3) nonprofit organization in the United States that works to improve health care quality through the administration of evidence-based standards, measures, programs, and ...

(NCQA) issued an update to the

Healthcare Effectiveness Data and Information Set The Healthcare Effectiveness Data and Information Set (HEDIS) is a widely used set of performance measures in the managed care industry, developed and maintained by the National Committee for Quality Assurance (NCQA). HEDIS was designed to allow ...

(HEDIS) for 2017, while the guideline remains for the patients aged 50 or over. A multi-target stool DNA test 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 Cost-effectiveness analysis (CEA) is a form of economic analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which assigns a monet ...

compared to colonoscopy or fecal occult blood testing. Three-year multi-target stool DNA test has been estimated to cost $11,313 per

quality-adjusted life year The quality-adjusted life year (QALY) is a generic measure of disease burden, including both the quality and the quantity of life lived. It is used in economic evaluation to assess the value of medical interventions. One QALY equates to one year ...

(QALY) compared with no screening.

Microbiology tests

Parasitic diseases such as

ascariasis Ascariasis is a disease caused by the parasitic roundworm '' Ascaris lumbricoides''. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may ...

hookworm Hookworms are intestinal, blood-feeding, parasitic roundworms that cause types of infection known as helminthiases. Hookworm infection is found in many parts of the world, and is common in areas with poor access to adequate water, sanitation ...

strongyloidiasis Strongyloidiasis is a human parasitic disease caused by the nematode called ''Strongyloides stercoralis'', or sometimes the closely related ''S. fülleborni''. These helminths belong to a group of nematodes called roundworms. These intestinal w ...

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 ''Rotavirus'' is a genus of double-stranded RNA viruses in the family ''Reoviridae''. Rotaviruses are the most common cause of diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotaviru ...

can also be found in stools.

Chemical tests

A fecal pH test may be used to determine

lactose intolerance Lactose intolerance is a common condition caused by a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pa ...

or the presence of an infection.

Steatorrhea Steatorrhea (or steatorrhoea) is the presence of excess fat in feces. Stools may be bulky and difficult to flush, have a pale and oily appearance, and can be especially foul-smelling. An oily anal leakage or some level of fecal incontinence may ...

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.

References