Newly published research paper demonstrates test inaccuracies due to sample holding time
Water management services company Phigenics LLC recently announced the publication of a research paper that demonstrates up to 33% false-positive test results for Legionella bacteria when following conventional sampling methods.
A false-positive result means the test indicated that Legionella was present in the water system at detectable levels when in fact it was below detectable levels at the time the sample was taken from the building water system. The greatest degree of error was found in utility water systems where 33% of 580 samples shipped from hundreds of building water systems showed false-positive results.
There were also a significant number of false-negative results observed from many thousands of shipped water samples transported from hundreds of building water systems. "Inaccuracy in Legionella Tests of Building Water Systems Due to Sample Holding Time" recently was published by Phigenics in Water Research, the official journal of the International Water Assn. (IWA).
"It provides robust statistical proof that results from conventional Legionella testing can be inaccurate and misleading," said Dr. William McCoy, chief technology officer of Phigenics and chair of ASHRAE Standards Project Committee 188, Prevention of Legionellosis Associated with Building Water Systems. "These inaccuracies can be eliminated by culturing the bacteria that causes Legionnaires' disease immediately after taking a water sample on site at the facility location. This simple change in procedure eliminates the potential of bacterial amplification or decline in water samples during transport to the laboratory. Shipping water samples to the laboratory has been shown to cause inaccurate or misleading results from many building water systems."