What is the role of antigen-antibody testing in the workup of Legionella pneumonia?

Updated: Sep 30, 2020
  • Author: Justina Gamache, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Answer

Urinary antigen testing for Legionella serogroup 1 organisms is accurate. However, as many as 30% of infections are not caused by serogroup 1 organisms. A Legionella serum antibody titer of 1:128 or more is suggestive of the diagnosis. Pneumococcal antigen tests for serum, urine, and saliva samples have been developed. Antigen-antibody testing has little clinical effect in an emergency department setting, although it may help in recalcitrant or unclear cases.


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