Sample6 DETECT/L: What Does AOAC Certification mean?
Last month, the Sample6 DETECT/L listeria environmental assay was certified by the AOAC. DETECT/L is the first in-shift non-enrichment test that the AOAC has ever certified. To our customers, this is a critical milestone, required for the adoption of a new diagnostic. Our advisor, David Acheson of The Acheson Group, describes it as “the gold standard in validation for food safety diagnostics and indicates a high standard of product that users can have confidence in.”
In this post, I would like to discuss what the AOAC certification means and what it tells us about the performance and capabilities of the DETECT/L assay.
What is the AOAC?
AOAC International, short for the Association of Analytical Communities, is an independent, third-party nongovernment and not-for-profit association, founded in 1884. The association includes international industry organizations, government agencies, research institutions, and individual scientists, who network, engage, and deliberate on methods and quality measurements. Based on this cross industry collaboration, AOAC develops voluntary consensus standards in order to promote trade and to facilitate public health and safety. AOAC has two programs, OMA and PTM. DETECT/L was certified under the PTM program.
What is involved in AOAC PTM certification?
AOAC PTM certification is designed to test the sensitivity, specificity and robustness of the
method in comparison to the industry standards. This involves proving performance in both model systems and laboratory methods. Let’s walk through each of the types of test, explain what they are intended to demonstrate and review how DETECT/L performed.
Inclusivity testing determines if the assay can detect a panel of bacterial targets as intended. This is critical for proving sensitivity and avoiding False Negatives. DETECT/L was tested on 50 strains of Listeria including 26 L. monocytogenes strains, 6 L. innocua strains, 6 L. ivanovii strains, 5 L. seeligeri strains and 5 L. welshimeri strains. Testing completed by a third party lab confirmed that DETECT/L was able to identify all 50 strains, proving the ability to correctly identify Listeria species.
Exclusivity testing determines if the assay detects any bacteria that it is not supposed to. This is critical for proving specificity and avoiding False Positives. A panel of 30 relatives of Listeria was tested with the DETECT/L assay. An outside lab verified that none of strains were detected. Therefore, DETECT/L does not detect any bugs that it is not supposed to.
Method comparison testing was used to determine if DETECT/L performs as well as the reference method, USDA culture. This test uses a model system in which Listeria cells are spotted on a stainless steel table and allowed to dry overnight. The spots are then sponged up and tested with both our assay and the USDA assay. Sample6 DETECT/L is able to provide results in less than 8 hours. USDA requires 6 days, meaning we had a long wait to find out how we compared! The third party lab found that DETECT/L was slightly more sensitive than the USDA method. While we waited for these results, we were reminded how critical it is that the industry have a faster test. We were recently in a plant that processed 50,000 lbs of product in an hour. In 6 days, 7,200,000 lbs of product pass through the plant. That is just too long to wait for results.
Robustness testing is intended to measure how sensitive the assay is to minor changes in the protocol. Will it still perform as promised if the operator accidently changes the volume of one of the reagents or the incubation temperature or the time of incubation? The testing showed that increasing or decreasing the incubation temperature by 2°C, slight variation in incubation time or increasing or decreasing the volume of the reaction by 20% had no impact on the performance of the assay. This indicates that the assay is quite robust and should be able to perform even when minor processing mistakes are made.
Stability testing is intended to determine if the kit performs consistently throughout its shelf life. To do this, kits that are at the beginning, middle and end of their shelf life are tested for their ability to detect Listeria. In all cases, DETECT/L performed perfectly indicating that there is no difference between a kit produced yesterday and one that has been on shelf for nearly all of its certified shelf life.
We are pleased with the performance of DETECT/L to date as are our pilot customers but we know there is more to do. We are hard at work on improvements to speed and ease of use. Are you ready to try DETECT/L?