Urine
Legionella
Legionella pneumophila antigen in urine; rapid screening.
€ 51,00
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Infections · Urine
Legionella pneumophila antigen in urine
Rapid test for a fragment of the Legionella bacterium in urine; in Legionnaires' disease often positive from the third day of illness.
At a glance
- Measured in urine
- In 1 test panel
- No special preparation
Explanation
Legionella pneumophila antigen in urine: what is measured?
Legionella is a bacterium that lives in water and that people take in by breathing in tiny water droplets, for example from a shower, a whirlpool or a cooling tower. During an infection, fragments of the bacterium, the antigen, end up in the urine. This test detects those fragments. Unlike an antibody test, it therefore does not measure the immune response but the bacterium itself, and this is possible from about the third day with symptoms. The test is mainly aimed at Legionella pneumophila serogroup 1, the type that causes most infections.
What can it detect?
- A current Legionella pneumonia (Legionnaires' disease) caused by Legionella pneumophila serogroup 1
- A sign that a pneumonia is caused by Legionella rather than by another bacterium
Result
What does the result mean?
Positive result
A positive result means that Legionella antigen was found in your urine. The specificity of the test is almost 100 percent, so in someone with pneumonia a positive result is a strong sign of legionellosis. Symptoms that fit it are high fever, coughing, shortness of breath, muscle pain and sometimes confusion or diarrhea. According to the notification criteria, a positive result is enough to report the disease to the GGD (municipal public health service), so that the search for the source can start.
Negative result
A negative result does not rule out legionellosis. The sensitivity depends on how severe the illness is and ranges from 50 to more than 90 percent; in severe pneumonia the test is usually positive, with a milder course more often negative. The test also finds almost only serogroup 1, so an infection by another Legionella species or serogroup can be missed. In the first two days with symptoms, the antigen may not yet be in the urine.
After an abnormal result
With a positive result, the doctor starts targeted antibiotics and, if needed, has a culture done on sputum or other respiratory material, which is needed to trace the source. Legionellosis is a notifiable group C disease under the Dutch Public Health Act (Wet publieke gezondheid): the doctor or laboratory must report it within one working day to the GGD (municipal public health service), which then investigates the possible source, for example a water system or cooling tower.
Reliability
How reliable is the test?
The urine test for Legionella antigen is simple, fast and very specific: according to the LCI guideline (RIVM) on legionellosis, almost 100 percent. The sensitivity ranges from 50 to more than 90 percent, depending on the severity of the illness. The result mainly means something in people with pneumonia; in someone without respiratory symptoms, the chance of legionellosis is so small that the test adds little. A culture remains important for tracing the source, because it allows the patient and the source to be compared with each other.
What can affect the result?
- The test is mainly aimed at Legionella pneumophila serogroup 1 and misses infections by other species or serogroups.
- The sensitivity is lower with a milder illness; a negative result does not rule out legionellosis.
- The antigen can usually only be detected from about the third day with symptoms.
- The antigen can remain in the urine for weeks after the infection, so a positive result does not always belong to the current symptoms.
Who it is for
Who is the test useful for?
Useful for
Useful with pneumonia, especially with a severe course, in people who have recently been abroad or have used a whirlpool or hot tub, or with a cluster of patients. Also in people at higher risk of a severe course, such as smokers, older people and people with a lung disease, diabetes, kidney disease or reduced immunity. Not useful in people without respiratory symptoms or as a general check-up: the test is designed to explain a pneumonia, not to screen.
How common is it?
In the Netherlands, 450 to 650 cases of Legionella pneumonia are reported to the GGD (municipal public health service) each year, about 2.6 to 3.8 per 100,000 inhabitants. About a third of these people were traveling during the incubation period and probably caught the infection abroad. It is estimated that 1 to 7 in 100 cases of pneumonia for which someone is admitted to hospital are caused by Legionella. Most reports are in summer.
RIVM/LCI guideline on legionellosis
Drawbacks and risks
- A negative result can give false reassurance: with a milder course or another Legionella species, the test misses the infection.
- Because the antigen can persist for weeks, a positive result with new symptoms can wrongly be attributed to Legionella.
Get tested
Legionella pneumophila antigen in urine: test panels
Legionella pneumophila antigen in urine is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
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