You can use immunochromatography tests for antigen detection in urine as a screening tool. If positive, your patient is most likely infected with Legionella pneumophila. Further identification (i.e. serotype of that Legionella strain) is not possible with the rapid tests. Antigens can be detected about 24 hrs following onset of infection but a patient may remain positive for Legionella antigen after infection has resolved. Saying this, it is important to put the actual clinical symptoms into consideration for a conclusive diagnostic. If the antigen test is positive, further diagnostics (e.g. culture or PCR from respiratory specimens) is warranted. However, if the immunochromatography test fails to detect antigen, this does not necessarily mean that the patient is not infected with Legionella. By the way, there are also immunochromatography tests available for other pathogens, e.g. pneumococcus, also from urine. In any case, please keep in mind that these immunochromatography tests are always rapid/screening tests and that sensitivity and specificity is not as high as for culture or for nucleic acid amplification tests.

Dear Dr Oliver

I am using Immunochromatography rapid test from Immunospark company, in our medical Microbiology lab, I have hardship to culture L. Pneumophila, therefore I tried to find some simple ways for screening patients for this infection. but I was not sure about its index in diagnosis. Also I requested for MTB rapid tests, I am woundring why these tests are not provided directly for screening from Phlegm BAL or other respiratory samples?!?

Dear Dr. Kafil, The Legionella antigen test I'am familiar with is the Alere BinaxNOW Legionella test. It can be used with urine and csf. I would assume that these immunochromatography tests may work with other  fluids like BAL, too, but have never been validated for this. Using BAL, the chance of getting positive results may be compromised by the high dilution of the specimen, though. However, I am not aware of any literature, describing the antigen test with other fluids than urine and csf.

Dear Dr Olivier 

So, This Positive Urine test indicates respiratory infection by Legionella ??

A positive urine test confirms the presence of antigen of Legionella in the urine. If the patient is suffering pneumonia, the positive test is indicative of respiratory Legionella infection (disease). You cannot use the antigen test for follow-up since Legionella antigen can be detected even when the patient has fully recovered. In other words, a positive urinary antigen test needs a clinical correlation (i.e. pneumonia) to indicate a respiratory Legionella infection.

Dear dr oliver

Thanks for you guide and helpfull comments