Table 1.

Stratification of disease severity associated with C. difficile colonization (44, 45).

Classification	Diagnostic criteria
Asymptomatic carriage/colonization	Positive identification of C. difficile (toxigenic or non-toxigenic) without clinical symptoms
Mild to moderate C. difficile infection (CDI)	≥3 unformed stools in 24 hours Positive identification of toxigenic C. difficile White blood cell (WBC) count <15,000 and serum creatinine levels <1.5X pre-morbid level
Severe CDI	Positive identification of toxigenic C. difficile and/or evidence of pseudomembranous colitis White blood cell (WBC) count ≥15,000 cells/μl, serum albumin <3 g/dl and/or serum creatinine level ≥1.5X premorbid level
Severe, complicated CDI (sometimes referred to as “fulminant”) (45)	Hypotension, shock, ileus, or megacolon Other systemic signs of severe infection (145) including: Admission to intensive care unit Altered mental status Fever ≥38.5°C WBC <2000 or >30,000/μl Lactate >2.2 mmol/L, or Evidence of end-organ damage Positive identification of toxigenic C. difficile
Recurrent CDI (rCDI)	Recurrence of symptoms within 8 weeks of successful C. difficile treatment