Legionella – Serum Antibody

Testing Indications

Contact your local Health Unit if you suspect a Legionella outbreak in your facility.

Timing of Specimen Collection

Acute phase (within 1  week before or after onset)

Convalescent phase (3-6 weeks after onset)

Limitations

Haemolysed, icteric, lipemic or microbially contaminated sera or plasma will not be tested.

Preparation Prior to Transport

Label the specimen container with the patient’s full name, date of collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Special Instructions

Centrifuge if using SST.

Specimens should be stored at 2-8°C following collection and shipped to PHO laboratory on ice packs.

Test Frequency and Turnaround Time (TAT)

The Legionella serum antibody testing is performed once weekly.  

Turnaround time is up to 5 days from receipt by PHO laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Specimens that are positive for Legionella are to be reported to Medical Officer of Health as per the Health Protection and Promotion Act.

An indirect Fluorescent Antibody (IFA) test is used to measure seroconversion, if present.

Interpretation

A four-fold seroconversion to 1:128 indicates recent infection while a standing titre of >=1:256 may indicate infection at some undetermined time.

The IFA is >80% sensitive and >90% specific.