What is the role of PCR assays 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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Answer

Answer

Polymerase chain reaction (PCR) has emerged as an important diagnostic tool for determining the etiology of CAP, particularly with regard to respiratory viruses and fastidious organisms, including Legionella, Mycoplasma, and Chlamydophila. [2] PCR is a very sensitive and specific method for isolating these pathogens. The source of specimen may affect the diagnostic yield of PCR assays; for instance, the detection rate of many pathogens, including Legionella and M pneumoniae, is higher with sputum samples than with nasopharyngeal aspirates. [60] However, nasopharyngeal samples remain useful, as many patients are unable to provide a quality sputum sample. The increasing commercial availability of various PCR assays (including multiplex) has allowed for increased implementation in the clinical setting. Multipathogen approaches are less expensive and more time consuming than testing each organism individually, although they may be complex to perform. Rapid molecular tests for respiratory viruses are also increasingly being developed with the goal of further shortening the time to diagnosis. [61]

Interpreting the significance of PCR detection of an organism known to colonize the upper airway or those that may be associated with protracted shedding, such as rhinovirus, remains a challenge. Quantitative PCR methods have shown some promise in improving interpretability of such findings. [62]


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