C. difficile infection.

C. difficile becomes established in the intestine. Technically, colonized individuals may or may not have CDI, since an individual with an infection is necessarily colonized by the organism. However, the term is often used in the literature to denote asymptomatic colonization.

Fraction of tested stool specimens that had a positive reference test and a negative result for the diagnostic method being evaluated. The false negative fraction is equal to one minus the sensitivity.

Fraction of tested stool specimens that had a negative reference test and a positive result for the diagnostic method being evaluated. The false positive fraction is equal to one minus the specificity.

Methods of amplifying (replicating) specific parts of genetic material (DNA) in samples usually using the polymerase chain reaction (PCR) followed by detection of the highly replicated gene fragment.

Accelerated rate of spore production.

Strains of CDI that include increased toxin production, an additional binary toxin, hypersporulation, and high-level resistance to fluoroquinolone antibiotics.²⁷

Test that is based on interactions between added animal antibodies against the specific substance to be detected, e.g. C. difficile toxins or glutamate dehydrogenase. Different tests use varying methods to isolate and detect the antibody/antigen complexes formed in the specimen being tested. Commonly referred to as enzyme immunoassay (EIA) in the literature.

Fraction of tested stool specimens that were negative for the diagnostic method being evaluated and negative on the reference test. Depends on the prevalence of toxigenic C. difficile in the tested specimens.

Therapies other than treatment with antibiotics for CDI, such as probiotics, prebiotics, monoclonal antibodies, and fecal flora reconstitution.

Fraction of tested stool specimens that were positive for the diagnostic method being evaluated and positive on the reference test. Depends on the prevalence of toxigenic C. difficile in the tested specimens.

Nondigestible foods that create environments healthy for bacteria growth.

Living microorganisms, including bacteria or yeast, which are believed to restore microbial balance to gastrointestinal flora when administered in adequate amounts.

Recurrence of symptoms within 8 to 10 weeks after cessation of specific antibiotic therapy, with exclusion of other enteropathogens and a positive diagnostic test for toxigenic C. difficile.¹¹⁹

Fraction of tested stool specimens that had a positive reference test and a positive result for the diagnostic method being evaluated. Sensitivity is also called the true positive fraction.

Definitions vary in the literature, but generally refer to a CDI diagnosis in combination with more complex manifestations of disease or in patients with other significant risk-factors such as age, signs of infections, or comorbidities.

Fraction of tested stool specimens that had a negative reference test and a negative result for the diagnostic method being evaluated. Specificity is also called the true negative fraction.