Combined Interpretations of the 2003, 2009, and 2016 Standards that apply to Volume 1 of the 2016 TNI Standard
Question: My question is regarding the Test Variability/Reproducibility section in the new 2016 standard. The verbiage essentially states to perform for methods that specify counts (i.e., cfu/100 mL or MPN/100mL)..." or other methods which specify a quantitative result." My question is, was the intent to hold labs accountable for performing this for IDEXX Quanti-tray as well? It is an MPN method; however, I did not feel the intent was to perform for this method but rather other MPN methods (e.g., multiple tube fermentation). Furthermore, if a laboratory is not obtaining any positive samples over the course of a month using this method, would they still be required to perform one? Standard methods instructs to perform this for plate counting methods, so I wanted to make sure the intent as to what methods to hold labs accountable for. TNI Response: The standard is clear on the inclusion MPN methods and this does not exclude Quanti-tray. Furthermore, the STD states 'duplicate counts shall be performed monthly'. It would be up to the lab to determine how they obtain the positive sample with which to perform the counts.
MODULE 5: MICROBIOLOGY TECHNICAL REQUIREMENTS
Section: 1.7.3.3