Pontiac fever can be confirmed by urine antigen or paired sera (blood specimens), but a negative test doesn’t rule out the diagnosis. It is often diagnosed clinically in the setting of other laboratory-confirmed legionellosis cases. Culture (isolating and growing the bacteria on special media) cannot be used to diagnose Pontiac fever.
Most people with Legionnaires' disease will have pneumonia (lung infection) since the Legionella bacteria grow and thrive in the lungs. Pneumonia is confirmed either by chest x-ray or on physical exam.
Several laboratory tests can be used to detect the Legionella bacteria within the body.
Urine Antigen Test
The most commonly used laboratory test for diagnosis is the urinary antigen test, which detects a part of the Legionella bacteria in urine (pee). If the patient has pneumonia and the test is positive, then the patient is considered to have Legionnaires' disease.
If the Legionella bacteria are cultured (isolated and grown on special media) from sputum (phlegm), a lung biopsy specimen, or various other sites, the diagnosis of Legionnaires’ disease is also considered confirmed.
Paired sera (blood specimens) that show a four-fold increase in antibody levels when drawn shortly after illness and several weeks following recovery, can also be used to confirm the diagnosis.
Images and logos on this website which are trademarked/copyrighted or used with permission of the trademark/copyright or logo holder are not in the public domain. These images and logos have been licensed for or used with permission in the materials provided on this website. The materials in the form presented on this website may be used without seeking further permission. Any other use of trademarked/copyrighted images or logos requires permission from the trademark/copyright holder...more
This graphic notice means that you are leaving an HHS Web site. For more information, please see the Exit Notification and Disclaimer policy.