Which tests may be useful in the diagnosis 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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For patients with severe CAP, patients being empirically treated for methicillin-resistant S aureus (MRSA) or Pseudomonas, or patients in whom a specific etiology is suspected, additional workup may be warranted, including the following: [7]

  • Sputum Gram stain and/or culture
  • Blood cultures
  • Serum sodium level
  • Serum transaminase levels
  • Lactic acid level
  • C-reactive protein (CRP)
  • Lactate dehydrogenase (LDH)
  • Molecular diagnostics, ie, polymerase chain reaction (PCR) testing
  • Urinary antigen testing for Legionella species

In special situations:

  • During influenza season, molecular assay for influenza
  • Serologic studies for M pneumoniae, C pneumoniae, Bordetella pertussis, C burnetii
  • Creatine phosphokinase (CPK)
  • Serum phosphorus level

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