OVERVIEW OF CHANGES TO THE TNI 2016 STANDARD

Below is an overview of the significant changes that have been made to the 2016 TNI Standard affecting Volume 3, General Requirements for Environmental Proficiency Test Providers. Also mentioned are other TNI Volumes when those changes directly affect the Proficiency Testing process. When the 2016 Standard is finalized we will be given an implementation date. At that point Waters ERA will initiate our work towards implementation of this new standard.

Accreditation to ISO/IEC 17043 Required

In addition to accreditation to the current TNI standard for every TNI FoPT which they will offer in their PT programs, all PT providers shall be accredited to ISO/IEC 17043:2010 General Requirements for Proficiency Testing by a TNI-approved PTPA. Given this new requirement 2016 Volume 3 was written to match this ISO format and any redundant requirements between the two documents were removed.

Removal of Appendix A

This appendix in the 2009 standard gave guidance on acceptable procedures for testing of homogeneity and stability of PT samples. It was determined to be redundant and had only been given as guidance in the current standard.

Removal of the 10% Maximum Verification Limit

Requirements for verification of aqueous chemistry analytes is still required to be within one-third of the laboratory acceptance limits. The requirement to limit the maximum allowed difference to 10% has been removed. It was determined that the 10% maximum was “arbitrary” and not statistically supported.

Removal of the 1/6 Repeatability Acceptance Limit

Requirement that the analytical method used for verification have a repeatability relative standard deviation of not more than one-sixth the acceptance limit was removed.

Revision of Homogeneity Testing Requirements

Homogeneity shall be verified using the procedure described in Appendix A or equivalent ability, as determined by the PTPA, to verify that differences between samples will not impact the laboratory evaluations has been dropped and replaced requiring PT providers to meet requirements found in Annex B, Section B1 through B3 of ISO/IEC 13528-2015(E).

Stability Testing given additional option

PT sample stability assessments shall be based on analytical data comparing the mean of a series of random samples analytically tested before the start of a study to the mean of a series of random samples analytically tested after the study close date. If the difference between the two means cannot be shown to affect an evaluation, then the analyte can be considered stable for the study period (suitable procedure given in Appendix A). This section was dropped and replaced with the following two options:

  1. The difference between the mean of the PT provider’s verification analyses and the mean of the PT provider’s stability analyses is within one-fifth of the laboratory acceptance limits.
  2. It can be demonstrated that the difference between the PT provider’s verification mean and the mean of the PT provider’s stability analyses does not affect laboratory evaluations.

Assigned Values for Quantitative Microbiology Changed

Requirement of PT provider’s to set assigned value for quantitative microbiology to the mean of verification and /or homogeneity testing has been replaced with having the assigned value equal to the study calculated mean.

Protozoan PT Requirements Added

Specification concerning assigned values, data evaluation and acceptance limit calculations have been added for the inclusion of Protozoan PT programs.

WETT Requirements Added

Previously not directly addressed, whole effluent toxicity testing (WETT) has sections added for assigned values, data evaluation and acceptance limit calculations.

PT Results Evaluation Changes

Generally speaking the standard is going back to the 2003 NELAC Standard criteria and in addition will now address evaluations of “>” results. 2016 TNI standard will evaluate results as follows:

For Assigned Values Greater Than the PTRL:

  • Results shall be scored “Acceptable” if the numeric value reported is within or equal to the established acceptance limit.
  • Results shall be scored “Not Acceptable” if one of the following is true:
    1. The numeric value is reported with a less than (<) sign;
    2. The numeric value reported is outside the established acceptance limits; or
    3. The numeric value is reported with a greater than (>) sign.

For Assigned Values Less than (<) PTRL:

  • Results shall be scored “Acceptable” ” if one of the following is true:
    1. The numeric value reported is less than the PTRL or
    2. The numeric value is reported with a less than (<) sign.
  • Results shall be scored “Not Acceptable” ” if one of the following is true:
    1. The numeric value reported is greater than or equal to the PTRL; or
    2. The numeric value is reported with a greater than (>) sign.

NOTE: This is a significant change from how Waters ERA has historically handled greater than results for quantitative microbiology sample evaluations. Selection of dilutions becomes even more critical so that greater than results are avoided.

No Evaluation Scoring:

  • A reported value shall be scored “No Evaluation” if it cannot be evaluated (e.g., alpha characters for quantitative test).
  • If an analyte in the PT sample is invalidated, the reported value shall be scored “No Evaluation” and the PT providers shall provide an explanation of the cause for invalidation in final evaluation report submitted to participant laboratories and the AB for which the laboratories designated submission of the report.

Summary Report for FoPT Table Evaluation

New section added requiring PT providers to make PT study statistics available at the request of the PTPEC to support development of the FoPT tables.

PT Reporting Requirements for TNI Labs under V1M1

Reporting requirements are changing back to using PTRLs. If the analytical result is a non-detect the laboratory shall report one of the following:

  1. <PTRL or
  2. <LOQ**

** NOTE: In the case where the laboratory LOQ is greater than the PTRL, if the laboratory chooses to report a value of < LOQ and the analyte is present above the PTRL, the result will be scored as “Not Acceptable” by the PT provider.

Initial Laboratory Accreditation for TNI Labs under V1M1

The opening date of the second study must be at least seven (7) calendar days after the closing date of the first. This is no longer based on analysis date. This is a change from the current 15 elapsed calendar days based on analysis date in the 2009 TNI Standard.


If you have questions regarding the changes to The NELAC Institute 2016 Standard, please contact Craig Huff, Waters ERA Senior Technical Manager, or Mike Blades, Waters ERA Technical Manager. As part of Waters ERA's continual support of The NELAC Instititute (TNI), Craig Huff and Mike Blades have spent many hours as members of various TNI committees. Craig Huff is a member of TNI's PT Expert Committee and Chair of the FoPT Format Subcommittee. Mike Blades is a member of TNI's FoPT Subcommittee and the specially formed Micro Subcommittee.