Which scoring systems are used to assess the severity of community-acquired pneumonia (CAP)?

Updated: Oct 31, 2019
  • Author: Stephanie L Baer, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Multiple scoring systems are available to assess the severity of CAP and to assist in deciding whether a patient should be hospitalized or admitted to the intensive care unit (ICU). Severe pneumonia is defined as having 1 major or 3 minor criteria. Major criteria include septic shock requiring vasopressors or respiratory failure requiring mechanical ventilation. Minor criteria include the following: [7]

  • Respiratory rate of 30 or more breaths per minute
  • PaO 2/FIO 2 ratio of 250 or less
  • Multilobar infiltrates
  • Confusion
  • Uremia
  • Leukopenia (WBC < 4000 cells/µl)
  • Thrombocytopenia (platelet count < 100,000/µl)
  • Hypothermia
  • Hypotension

The Pneumonia Severity Index (PSI) is preferred over the CURB-65 (confusion, uremia, respiratory rate, low blood pressure, age >65 years) for determining outpatient versus inpatient treatment. Patients with PSI class IV-V may need hospitalization or more intensive in-home services. ICU admission is recommended for any patient who requires mechanical ventilation or vasopressors. Admission to higher-acuity care or critical care should also be considered in patients with 3 or more minor risk factors for severe pneumonia.

Other scoring systems may also be helpful in certain populations to predict the severity of CAP. The SMART-COP score emphasizes the ability to predict the need for ventilator or vasopressor support and includes systolic blood pressure, multilobar infiltrates, serum albumin levels, respiratory rate, tachycardia, confusion, oxygenation, and pH level. The A-DROP (age, dehydration, respiratory failure, orientation, systolic blood pressure) is also a severity score. Recently, an expanded CURB-65 has been shown to improve prediction of 30-day mortality. It includes LDH, thrombocytopenia, and serum albumin, along with the traditional CURB-65, and has been shown to have better prediction accuracy. The value of adding biomarkers in addition to the above scoring systems to identify patients at risk of worse outcomes is being studied. [10, 11, 12, 13, 14]

More recent research indicates that the use of biomarkers, specifically procalcitonin and CRP, may further increase the ability to identify patients at increased risk for worse outcomes, although this remains controversial. A positive pneumococcal urine antigen result has been associated with a good prognosis. [15] Certain prior pulmonary pathology, such as past infection with pulmonary tuberculosis, may increase the risk of mortality. [16]

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