Table 3.

IDSA/ATS Criteria for Defining Severe CAP^a,28.

Minor criteria	Major criteria
Respiratory rate ≥30 breaths/min PaO2/FIO2 ratio ≤250 Multilobar infiltrates Confusion/disorientation Uremia (BUN ≥20 mg/dL) Leukopeniab (WBC <4000 cells/µL) Thrombocytopenia (platelet count <100 000/µL) Hypothermia (core T < 36 °C) Hypotension requiring aggressive fluid resuscitation	Septic shock with need for vasopressors Respiratory failure requiring mechanical ventilation

Abbreviations: IDSA/ATS, Infectious Diseases Society of America/American Thoracic Society; CAP, community-acquired pneumonia; Pa_O2, partial pressure of arterial oxygen; FI_O2, percentage of inspired oxygen; BUN, blood urea nitrogen; WBC, white blood cell count.

^aValidated definition of severe CAP includes either 1 major criterion or ≥3 minor criteria.

^bDue to infection alone (ie, not chemotherapy induced).