Diagnostic Testing for Legionnaires’ Disease and Pontiac Fever
If an outbreak of Legionnaires’ disease or Pontiac fever is suspected, it is of paramount importance to obtain a definitive diagnosis in all those who may have fallen ill. To do this there are a number of preferred tests that are used to assist in identification and diagnosis and these include the urinary antigen test, but also obtaining cultures, usually from the patients mucus to determine if Legionella bacteria is present.
What is a urinary antigen test for Legionnaires’ disease?
A urinary antigen test will help to identify whether any Legionella bacteria can be found in a sample of the patient’s urine. In many cases, a positive test will indicate Legionnaires’ disease is present. However, there are instances where a test can be negative, and yet the patient is still suspected of having the disease (often because of the various symptoms they may have). In this case, those treating the patient would usually request a culture test.
What is a culture test?
A culture is a sample that is allowed to grow – in this case, to see whether Legionella bacteria are present in the patient. A number of things can be used to create a culture. Often, respiratory secretions (mucus) are used to try and identify any bacteria present. However, pleural fluids and/or lung tissue might also be used in some circumstances.
Testing for Legionnaires’ disease - which test is best?
Although the urinary antigen test does not always flag cases of Legionnaires’ disease or Pontiac fever, it is still the go-to test in most cases, at least initially.
The urinary antigen test does have the advantage of providing a quick result, usually on the same day it is performed. However, it will only identify cases of Legionnaires’ disease that result from L. pneumophila serogroup 1. If another form of the bacteria is responsible for the disease, a negative result will be obtained.
On the other hand, while the culture option is quite sensitive, it takes around five days to grow. This means there is a period of waiting involved before a definitive result can be obtained.
The importance of proper testing for Legionnaires’ disease and Pontiac fever
There are occasions when accurate testing for Legionnaires’ disease and Pontiac fever can actually help identify the source of the outbreak. In a sense, the tests completed, and their results, will help investigators locate the source and hopefully prevent other cases from occurring.
Such diagnostic tests are also likely to become more refined and more accurate over time, but as of now, we have several methods that can be used to diagnose patients so they can receive appropriate treatment for Legionnaires’ disease or Pontiac fever.
Expert Legionella testing and risk management support
To find out more about our expert Legionella testing (water sampling) and risk management support services please contact us on 0161 877 0586 (Manchester) or 0203 637 47 48 (London).
152 City Road
London EC1V 2NX
Tel: +44 (0) 203 637 47 48
Unit B Badex Building
Manchester M17 1AY
Tel: +44 (0) 161 877 0586
For additional information about the diagnosis of Legionnaires' disease … here