LEGIONELLA, ANTIGEN, URINE - (U)

Test Code: LUA

Test Indications:
Legionella spp. are responsible for approximately 3% of community-acquired pneumonia cases in Canada.  Risk factors for infection with Legionella spp. include age ≥50 years, smoking, chronic lung disease, immune system disorders due to disease or medication, systemic malignancy, underlying illness such as diabetes mellitus, renal failure, or hepatic failure, recent travel with an overnight stay outside of the home, and exposure to hot tubs.  Testing for Legionella is indicated in more severely ill patients with community-acquired pneumonia, in patients with pneumonia and specific risk factors for Legionella spp. infection, and in the setting of a possible outbreak.  The treatment regimens for community-acquired pneumonia currently recommended in North America provide empiric coverage against Legionella spp.  When ordering this test, the clinician should carefully consider whether a positive or negative test result will alter clinical management.

Recommendations:
There are strict criteria for testing.  Testing is indicated for inpatients with community-acquired pneumonia and one of the following:
1.1 - ICU with community-acquired pneumonia
1.2 - Alcohol use disorder
1.3 - Travel within the last 2 weeks
1.4 - Pleural effusion
1.5 - Failed therapy
1.6 - Solid organ or hematological transplant patient
Failure to indicate at least one of the above testing criteria in the clinical history field of the Shared Health Microbiology Requisition will result in specimen rejection.
No more than one specimen every 5 days will be accepted, and no more than 3 per admission without consultation with the site microbiologist on call.
Clearly indicate on the microbiology requisition the specimen type and the test requested (Legionella antigen). 
Note that testing for other indications not covered above in 1.1 to 1.6 (e.g., suspected community outbreak) may be approved on a case-by-case basis by consulting the site microbiologist on-call.

Patient Preparation Instructions:
Collect a random urine specimen in a standard container.  The specimen may be obtained by having the patient void into a container (midstream sample not required) or from an indwelling catheter (when present).
Accurate patient identification must be made prior to sample collection.  Patient identification should be done in accordance with site policy.
Samples and requisitions must be labeled/completed in accordance with the Shared Health Specimen Acceptance Policy.

_SH Microbiology - Provincial Requisition (R250-10-06)

A descriptive report will be sent.  The test is reported as positive or negative.

Test Limitations:
A positive test result does not necessarily indicate that a patient's current presentation is due to infection with Legionella.  Legionella antigens may be detectable in urine for up to a year after an episode of Legionella pneumonia or Pontiac fever.  A positive result may indicate past or present infection and is not a definitive result without other supporting evidence.
A negative test result does not completely rule out infection with Legionella spp.  The assay will only detect Legionella pneumophila serogroup 1 and cannot be used to reliably identify infections caused by other serogroups or other Legionella spp.  Antigen may not be detected early in infection or if antigenuria is below the limit of detection, therefore a negative test also does not rule out early infection with Legionella pneumophila serogroup 1.

Daily

Specimen Handling:
Transport to the laboratory as soon as possible.
A preservative is not required, but boric acid is the only acceptable preservative if one is used.
The sample may be stored at room temperature ≤24 hours, at 2-8°C for up to 14 days, or at -10 to -20°C if testing will be delayed for longer periods.  Ensure samples that are being sent to a referral laboratory are packaged in accordance with Transport of Dangerous Goods recommendations for diagnostic samples.