Clostridium difficile, also known as "C. diff," is a species of bacteria that causes severe diarrhea and other intestinal disease when competing bacteria in the gut have been wiped out by antibiotics (see Wikipedia entry). In rare cases a C. diff infection can progress to toxic megacolon which can be life-threatening. In a very small percentage of the adult population C. difficile bacteria naturally reside in the gut. Other people accidentally ingest spores of the bacteria while patients in a hospital or nursing home.
True positive (for Gold standard cases): C. diff antigen / antibody positive or colonoscopy/flex sig positive for C. diff.
True positive (for Silver standard cases): the doctor believes they had C. diff colitis and treated them with an appropriate course of oral vancomycin (vancocin) or metronidazole (flagyl)