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Combined Interpretations of the 2003, 2009, and 2016 Standards that apply to Volume 1 of the 2016 TNI Standard

Section: Volume 3, 5.9.3

Question:  The result for EDB of <0.500ug/L was scored "not acceptable", against the true value of 0.299ug/L and limits of 0.179-0.419ug/L.  This result is not identified as consideration for unacceptable criteria. We disagree and feel that this result should be scored acceptable.  0.299ug/L is less than 0.500ug/L.

TNI Response:  Based upon current acceptance criteria, the lab result for the analyte provided in the problem statement was correctly scored as not acceptable. The FoPT tables include a footnote that states, "Proficiency Testing Reporting Limits (PTRLs) are provided as guidance to laboratories analyzing NELAC PT samples. These levels are the lowest acceptable results that could be obtained from the lowest spike level for each analyte. The laboratory should report any positive result down to the PTRL. It is recognized that in some cases (especially for analytes that typically exhibit low recover) that PTRL may be below the standard laboratory reporting limit. However, the laboratory should use a method that is sensitive enough to generate results at the PTRL shown..." The laboratory should be aware of and take into account the corresponding PTRL for each analyte before reporting any PT results.  The < value would be valid under the 2009 standard.  The 2016 standard reintroduces PTRLs, and this the SIR is still valid for 2016.  There are significant differences between the 2003, 2009 and 2016 standards.

Question:  Based upon a question from a customer I checked the FOT tables and NELAC Chapter 2 and I can’t find a requirement for evaluation of “less than” (<) values.  This was in the Criteria Document and I think was supplemented by a NELAC Board policy both or which would be invalid now.  If you agree, I think the PT Board needs to implement a Policy on “less than” reporting immediately to fill the gap until the TNI Standard, which is very poor, in this area is implemented.

TNI Response:  The 2009 standard has explicit language regarding < values.  The 2016 standard reintroduces PTRLs, and has different language regarding < values.  There are significant differences between the 2003, 2009 and 2016 standards.