Antigen excretion may begin as early as 3 days after onset of symptoms and persist for up to one year.
A negative result indicates a presumptive negative for Legionella pneumophila serogroup 1 antigen in urine, suggesting no recent or current infection.
Infection due to Legionella cannot be ruled out since other serogroups and species may cause disease, the antigen may not be present in urine in early infection, or the level of antigen present in the urine may be below the detection limit of the test.
Culture is recommended to detect causative agents other than Legionella pneumophila serogroup 1 and to recover L. pneumophila serogroup 1 when antigen is not detected in the urine.
A positive result suggests current or past infection and is not definitive for infection without other supporting evidence.