Stool antigen test

A diagnostic assay that detects proteins from pathogens in a stool sample. It is used to identify active gastrointestinal infections, including Helicobacter pylori and Clostridioides difficile.

Antigen–antibody interaction: Specific binding between an antigen and an antibody through complementary molecular surfaces. Test antibodies bind pathogen proteins in the stool and produce a detectable signal.
Helicobacter pylori stool antigen test: A stool assay that detects Helicobacter pylori antigens to diagnose infection or assess eradication after treatment. This is a common use of stool antigen testing, including follow-up after therapy.
Stool culture: A laboratory method that grows microorganisms from stool to identify viable bacterial pathogens. Culture can recover living bacteria, whereas antigen tests detect proteins without requiring growth.
Stool specimen: A sample of feces collected for laboratory examination or diagnostic testing. The sample's collection, storage, and consistency can affect antigen measurement.
Antimicrobial stewardship: Efforts to use antimicrobial medicines appropriately while preserving their effectiveness and limiting harm. Reliable pathogen detection can help target treatment rather than use antibiotics without evidence.
Enzyme immunoassay: An immunoassay that uses an enzyme-linked reagent to generate a measurable signal when target molecules are present. Many stool antigen assays use enzyme-linked antibodies to reveal pathogen proteins.
Clostridioides difficile infection: An intestinal infection caused by toxin-producing Clostridioides difficile, often following disruption of the gut microbiota. Some diagnostic algorithms detect C. difficile antigens alongside its toxins.
Polymerase chain reaction: A laboratory technique that amplifies specific DNA sequences to enable their detection. PCR detects genetic material rather than the pathogen proteins targeted by antigen assays.
Sensitivity and specificity: Measures of how well a test identifies people with a condition and excludes those without it. These properties describe the frequency of missed infections and false-positive results.
Test of cure: A follow-up test used to determine whether treatment has successfully eliminated an infection. H. pylori stool antigen testing can confirm eradication after an appropriate post-treatment interval.

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