Severe community-acquired pneumonia. Assessment of severity criteria

Am J Respir Crit Care Med. 1998 Oct;158(4):1102-8. doi: 10.1164/ajrccm.158.4.9803114.


The purpose of the study was to validate the criteria used in the guidelines of the American Thoracic Society (ATS) for severe community-acquired pneumonia (CAP). Severe pneumonia was defined as admission to the intensive care unit (ICU). Overall 331 nonsevere (84%) and 64 severe cases (16%) of CAP were prospectively studied. Mortality was 19 of 395 (5%) and 19 of 64 (30%), respectively. Single severity criteria as well as the ATS definition of severe pneumonia were assessed calculating the operative indices. A modified prediction rule including minor (baseline) and major (baseline or evolutionary) criteria was derived. Single minor criteria at admission had a low sensitivity and positive predictive value. Defining severe pneumonia according to the ATS guidelines had a high sensitivity (98%). However, specificity and positive predictive value were low (32% and 24%, respectively). A modified prediction rule (presence of two or three minor criteria [systolic blood pressure < 90 mm Hg, multilobar involvement, PaO2/FIO2 < 250] or one of two major criteria [requirement of mechanical ventilation, presence of septic shock]) had a sensitivity of 78%, a specificity of 94%, a positive predictive value of 75%, and a negative predictive value of 95%. The ATS definition of severe pneumonia was highly sensitive but insufficiently specific and had a low positive predictive value. Our suggested modified rule had a more balanced performance and, if validated in an independent population, may represent a more accurate definition of severe CAP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Blood Pressure / physiology
  • Community-Acquired Infections / classification*
  • Community-Acquired Infections / mortality
  • Community-Acquired Infections / surgery
  • Critical Care
  • Disease Progression
  • Female
  • Forecasting
  • Humans
  • Lung / physiopathology
  • Male
  • Middle Aged
  • Patient Admission
  • Pneumonia / classification*
  • Pneumonia / mortality
  • Pneumonia / surgery
  • Practice Guidelines as Topic
  • Predictive Value of Tests
  • Prospective Studies
  • Renal Insufficiency / complications
  • Reproducibility of Results
  • Respiration, Artificial
  • Respiratory Insufficiency / complications
  • Sensitivity and Specificity
  • Severity of Illness Index*
  • Shock, Septic / complications
  • Spain / epidemiology
  • Survival Rate