What is the role of serology in the evaluation for community-acquired pneumonia (CAP)?

Updated: Oct 31, 2019
  • Author: Stephanie L Baer, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Serology has been replaced by more rapid PCR-based assays in many settings; serology was historically useful in identifying fastidious organisms, particularly when dealing with pathogens that have potential epidemiologic implications (ie, epidemic or biohazard situations), such as B pertussis, M pneumoniae, L pneumophila, or C burnetii. Serologic diagnosis is based on a 4-fold or greater increase in titers between acute- and convalescent-phase serum specimens so is generally not useful in the acute-care setting. A significantly elevated IgM titer (typically present in the acute phase of infection) may help support a diagnosis, and some experts have suggested that combining IgM and nucleic acid amplification testing may be the optimal method for diagnosing M pneumoniae infection. [56]

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