Legionella – Serum Antibody

Testing Indications

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

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Legionella – Serum antibody

Whole blood or serum

5.0 ml blood or 1.0 ml serum

Blood, clotted – vacutainer tubes SST1

Timing of Specimen Collection

Acute phase (within 1  week before or after onset)

Convalescent phase (3-6 weeks after onset)


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.

Requisitions and Kit Ordering

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.


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.

Test Methods

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


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.

Mis à jour le 13 janv. 2020