Cytotoxicity assay
C. difficile toxins have a cytopathic effect in cell culture, and neutralization of any effect observed with specific antisera is the practical gold standard for studies investigating new CDI diagnostic techniques. Toxigenic culture, in which organisms are cultured on selective media and tested for toxin production, remains the gold standard and is the most sensitive and specific test, although it is slow and labor-intensive. Toxin ELISA
Assessment of the A and B toxins by enzyme-linked immunosorbent assay (ELISA) for toxin A or B (or both) has a sensitivity of 63–99% and a specificity of 93–100%.Previously, experts recommended sending as many as three stool samples to rule out disease if initial tests are negative, but evidence suggests repeated testing during the same episode of diarrhea is of limited value and should be discouraged. C. difficile toxin should clear from the stool of somebody previously infected if treatment is effective. Many hospitals only test for the prevalent toxin A. Strains that express only the B toxin are now present in many hospitals, however, so testing for both toxins should occur. Not testing for both may contribute to a delay in obtaining laboratory results, which is often the cause of prolonged illness and poor outcomes. Other stool tests
Stool leukocyte measurements and stool lactoferrin levels also have been proposed as diagnostic tests, but may have limited diagnostic accuracy. PCR
Testing of stool samples by real-time polymerase chain reaction is able to detect C. difficile about 93% of the time and when positive is incorrectly positive about 3% of the time.
Clostridioides difficile infection
  (CDI or C-diff), also known as Clostridium difficile infection, is a symptomatic infection due to the spore-forming bacterium Clostridioides difficile. Symptoms include watery diarrhea, fever, nausea, and abdominal pain. It makes up about 20% of cases of antibiotic-associated diarrhea. Antibiotics can contribute to detrimental changes in gut microbiota; specifically, they decrease short-chain fatty acid absorption which results in osmotic, or watery, diarrhea. Complications may include pseudomembranous colitis, toxic megacolon, perforation of the colon, and sepsis.Clostridioides difficile infection is spread by bacterial spores found within feces. Surfaces may become contaminated with the spores with further spread occurring via the hands of healthcare workers. Risk factors for infection include antibiotic or proton pump inhibitor use, hospitalization, other health problems, and older age. Diagnosis is by stool culture or testing for the bacterias DNA or toxins. If a person tests positive but has no symptoms, the condition is known as C. difficile colonization rather than an infection.Prevention efforts include terminal room cleaning in hospitals, limiting antibiotic use, and handwashing campaigns in hospitals. Alcohol based hand sanitizer does not appear effective. Discontinuation of antibiotics may result in resolution of symptoms within three days in about 20% of those infected. The antibiotics metronidazole, vancomycin or fidaxomicin, will cure the infection. Retesting after treatment, as long as the symptoms have resolved, is not recommended, as a person may often remain colonized. Recurrences have been reported in up to 25% of people. Some tentative evidence indicates fecal microbiota transplantation and probiotics may decrease the risk of recurrence.C.