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Newly published research paper demonstrates test inaccuracies due to sample holding time
Phigenics LLC, a water management services company, 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 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," was recently published by Phigenics in Water Research, the official journal of the International Water Association (IWA).
"The impact of the research is significant in that it provides robust statistical proof that results from conventional Legionella testing can be inaccurate and misleading," says 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 onsite 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."
"We are predicting significant increases in Legionella testing over the coming years in commercial and institutional markets due to new Legionella Hazard Analysis and Critical Control Point (HACCP) standards such as ASHRAE Standard 188P and others that are scheduled for official publishing over the next twelve months or so," says Ashton McCombs, president of Phigenics. "This research is very important because the last thing anyone wants is to be making Legionella treatment and control decisions based on inaccurate testing results."
"It is possible to culture bacteria immediately upon taking a water sample onsite at the facility location, and thereby completely eliminate testing inaccuracies caused by water sample transit time," says Dr. McCoy. "The problem historically has been that it was not commercially practical to implement onsite cultures at any scale. This is an important problem that Phigenics has solved by offering a field practical method to immediately start the culture onsite. Instead of shipping a water sample, the user ships the cultured bacteria. Starting the culture immediately also significantly reduces the time required before test results can be reported to the user. "