False-Negative, Pathogenic-Test Results Are Higher Than You'd Think

By Laurel Maloy, contributing writer, Food Online

Recent findings by the American Proficiency Institute for foodborne-pathogen testing don’t bode well for food safety or consumer confidence

The American Proficiency Institute (API) conducts proficiency testing (PT) in regard to analysis of foodborne pathogens. Admittedly, you will hear complaints about the number of false-positive tests that are costly, time consuming, and just plain annoying. You hear much less about false-negative tests, which are actually more troubling; these negative pathogenic studies enable contaminated food to reach the consumers’ dinner tables. Today, the technology exists to quickly and accurately test for foodborne pathogens. However, what is missing is the attention to detail and the due diligence required to produce accurate test results.

As a rule, PTs are performed just two or three times a year; sometimes quarterly. Then again, with the implementation of FSMA and increased focus on food safety, the number of PTs is likely to grow. The argument can be made that food safety is everyone’s business, but in today’s world, food safety has taken on an ever-more specialized role. Now, more than ever, food safety is everyone’s responsibility; today’s regulations and statutes require more targeted training for a wider range of personnel.

Lab accreditation, required by FSMA, will be driving both improved technology and the requirement for lower, false-negative numbers. Third-party lab accreditation is also being advocated for by groups such as GFSI and the Food Laboratory Alliance.  According to the API study, currently, and for the better part of 13 years prior to 2013, false-negative, pathogenic testing has maintained an average 6.6 percent error rate. During the same period of time, false-positive testing averaged 3.1 percent. The old adage, “Better safe than sorry” definitely applies here. Any false-negative test is one too many. As irritating as they are, a false-positive test does little harm, but not when compared to the possible injury a false negative can do.  Unfortunately, false-negative results are not discovered until a foodborne-illness outbreak is identified or a PT is performed. Only then are the testing procedures put under a microscope and potential fixes identified and applied.

Tom Weschler of Strategic Consulting says in his past experience, while in charge of an environmental testing lab, PTs were routinely performed in-house, and therefore no secret. Management was aware of the upcoming PT and tasked the most-proficient personnel to perform the testing procedures. He goes on to ask if the purpose is to evaluate the entire lab. If so, shouldn’t all lab operators and protocols be examined? In the same vein, Weschler points out that if the best of the best are performing the testing protocols, shouldn’t the number of false-positive or false-negative tests be fewer? This is contrary to what API found.

API, in its study entitled Pathogen Detection in Food Microbiology Laboratories: An Analysis of Proficiency Test Performance, published the following results, compiled from 39,500 PTs conducted in U.S. labs between 1999 and 2012:

• E. coli O157:H7 — false-negative results ranging from 3.3 to 14.0 percent
• Salmonella — 1.9 percent to 10.6 percent
• Listeria monocytogenes — 3.4 percent to 11.0 percent
• Campylobacter — 0 percent to 19.8 percent

Food Plant Labs (FPLs) and Food Contract Labs (FCLs) should be doing their utmost to ensure the lowest-possible, false-negative results as it is not just a source of pride and revenue. Setting up new and more-stringent protocols for testing now will hold facilities in good stead as accreditation becomes a fact of life.