What is the role of serologic tests in the diagnosis of Legionella infection?

Updated: Nov 13, 2018
  • Author: Mobeen H Rathore, MD, CPE, FAAP, FIDSA; Chief Editor: Russell W Steele, MD  more...
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Serologic tests for Legionella antibodies

  • Serologic assays are not helpful in clinical decision making but are valuable for epidemiologic studies.

  • Confirmation of legionellosis requires a 4-fold or greater rise in antibody titer in paired acute and convalescent indirect fluorescent antibody (IFA) tests obtained 4-8 weeks apart.

  • A single elevated titer greater than 1:256 does not confirm a diagnosis of Legionnaires disease; titers of 1:256 or more are found in 1-16% of healthy adults and children.

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