The
accuracy of food microbiology laboratories when detecting or ruling out the
presence of E.coli 0157:H7, Salmonella spp., Listeria
monocytogenes and Campylobacter
jejuni remains concerning, according to a study.
The
analysis of nearly 40,000 proficiency test results over the past 14 years found
that false negative and false positive results are found on a routine basis.
A false
negative is when pathogens are not detected but are found in the food and a
false positive report shows the pathogens are there when they are not.
Pathogen
results: The study found that food laboratories report false negatives of 9.1%
for Campylobacter and 4.9% for Salmonella on average. The false
positive rate, also on average, is 3.9% for Salmonella
spp., and 2.5% for both E. coli
and L. monocytogenes.
"There
is concern when laboratories report that pathogens are not found in a food
sample, when in fact they are there," explained Christopher Snabes, lead
author on the study. "This is known as a 'false negative'. Similar
concerns arise when a laboratory reports a 'false positive' suggesting that
pathogens are in the food sample, when indeed they are not."
Study
details: The study was conducted by the American Proficiency Institute (API)
which is a private institute that supplies proficiency testing programs for
food laboratories and clinical laboratories. Currently, food laboratories are
not required to assess the accuracy or quality of their tests, said the
institute. API offers proficiency testing (PT) which looks for the presence or
absence of a substance in a qualitative test, and it may require an enumeration
response, or quantitative test.
The Food
Safety Modernization Act addressed model laboratory standards and laboratory
accreditation as components of the law. Once rules are promulgated, it is
anticipated that all food laboratories will need to ensure that their
personnel, and the test methods they use, are in compliance with the law, said
API.
The
research was presented as part of the 2013 General Meeting of the American
Society for Microbiology held this month in Denver, Colorado.
Source: Food
Quality News
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