What is Hydrosense Legionella Test

Hydrosense Legionella Test is a simple test that can be used for routine monitoring of all types of domestic water systems.

  • The test can be performed anywhere.
  • The test can be stored at room temperature for up to 18 months.
  • The test does not require the use of any extra equipment or safety equipment.
  • The test takes about 30 minutes from start to result.
  • The test has a proven efficacy which is more than good enough to cover routine monitoring.
  • The test gives a qualitative answer indicating positive/negative.

The test functions with Lateral Flow Technology (LFT) which is a common process for quick and simple diagnostics at hospitals, and is comparable to a pregnancy test. Explained simply this is antibody-antigen reaction that occurs on a cellulose strip which the sample material is flowing over in a determined direction. The reaction happens against specific markers, often proteins, existing on the surface of the bacterium.

Using the Hydrosense Legionella Test you will be able to obtain three results:

  • Reaction in the control field only, which indicates that the sample is NEGATIVE for Lpsg1 and the test has been carried out correctly.
  • No reaction on any of the fields, which indicates that something is wrong with the test strip, the sample material, or that the procedure has not been followed correctly, the test is INCONCLUSIVE.
  • Reaction on the control field and the test field, which indicates that the sample is POSITIVE for Lpsg1 and the test has been carried out correctly.

The following action should be taken based on the result:

  • A NEGATIVE result is logged upon test completion and no further action is required.
  • An INCONCLUSIVE result needs to be repeated until a positive or negative result is obtained, log all details on where the inconclusive test was taken.
  • A POSITIVE result means performing a full disinfection of the entire facility and new samples taken until a negative result is achieved, the whole process is logged. Norsesene can be contacted for help with disinfection process.

Validating and approval

The test has been validated through KWR Water Research Institute in the Netherlands, which is a publicly supported institute with internationally recognized expertise on use of fresh water for various purposes. Through a project that compared several methods for testing legionella in water samples Hydrosense Legionella Test gave good results compared to standard laboratory tests. The Hydrosense Legionella Test was better than culturing when compared on detection of Legionella pneumophila serogroup 1 (Lpsg1), and compared favourably with genetic tests (PCR) under the same conditions. In addition to this test, Nalco, an international water treatment company, have validated the test for use in their work. This validation has results good enough to approve it for use as a quick diagnostic test at hospital diagnostic laboratories in Norway.

The Norwegian Institute for Public Health (FHI) have also accepted the test as a supplement to accredited laboratory testing. “Concerning the test kit Hydrosense for rapid diagnostics of L. pneumophila serogroup 1 in water samples. Based on the test results given in the KWR report “A new method of screening cooling waters and process water for Legionella pneumophila” (KWR 2009.004, May 2009) we view Hydrosense as useable as a supplement to accredited analysis to monitor development of Legionella in water systems. The method is, however, limited to detection of L. pneumophila serogroup 1 and will therefore not detect any other legionella variants, which can also be pathogenic to humans. Serogroup 1 is however, the definitively most common Legionella variant when considering Legionnaire’s Disease.”

As the quote from FHI indicates, the major downside to the test is that it only detects Legionella pneumophila serogroup 1. This is, however, the most common bacteria when Legionnaire’s Disease is diagnosed, and it has been indicated that if legionella exists in a water system this variant will be one of those found. Do also note that the Hydrosense Legionella Test is not an accredited test, and is only intended as a supplement to be used in addition to accredited testing methods where this is necessary. However, in most places where legionella tests should be used there is no requirement for accredited testing, in this places the Hydrosense Legionella Test can be used as the only routine monitoring test.

The Hydrosense Legionella Test also has some faults concerning epidemiology and tracking infection sources. Since the answer is qualitative neither amount, though it is possible to get a rough estimate using the app, or a genetic profile can be obtained. Both can be very important in tracking infection sources and it is recommended that a sample is sent to a laboratory when high amounts of legionella are indicated.

Forebygging av legionellasmitte – en veiledning (PDF in Norwegian only)

Validering of the test (PDF, Norwegian)