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Standard Interpretation

Standard: 2003 NELAC
Section: Appendix E.3.2.1 / Chapter 2 2.6
Link to relevant standard


2. A similar [to the request regarding section 2.6] but more difficult situation occurs with the evaluation of microbiological data sets. In the case of quantitative microbiology, the NELAC 2003 Standard Chapter 2 Appendix E Section 3.2.1 appears to authorize the PT provider to use alternative evaluation criteria where 20 valid data points are not available. The Appendix appears to be in direct conflict with Chapter 2 Section 2.6 noted above which clearly states that there are no exceptions. The APG procedure in this case was to supplement available interlaboratory data with internal testing data run by the same method as the laboratories. The A2LA auditor found this to be inappropriate. We do not disagree with the auditors in this instance; however, Chapter 2 Appendix E Section 3.2.1 requires any alternate procedure to be approved by the PTOB. Clearly, the responsibility to providing acceptable evaluation criteria lies with the NELAC PT Board as noted in Chapter 2 Section 2.6 and not with either the PT provider or A2LA. In an effort to get appropriate guidance from A2LA as to available acceptable alternate procedures, we requested guidance from the A2LA microbiological auditor. She provided no recommendation on alternative acceptable procedures. Similarly, we requested guidance from the statistical auditor whose comment was that other providers have procedures but that he was not allowed to provide consultation.

It appears to APG that if an alternative quantitative microbiological evaluation procedure must be approved by the PTOB that they then have an obligation to provide guidance on an acceptable proceed. However, it seems inappropriate for A2LA to accept responsibility for setting NELAC acceptance criteria when that function is vested in the NELAC PT Board by the 2003 NELAC Standard. Therefore, in order to meet the requirement of Chapter 2 Appendix E 3.2.1 alternative guidance must be provided since it is also not the responsibility of the PT provider to establish NELAC evaluation criteria.


(Proficiency Testing Board / NELAP Board, 10-11-09)

The information in specific appendices, i.e. Appendix E for Microbiology, takes precedence over the information in the general standard, where conflicts exist. Therefore, Appendix E 3.2.1 must be followed and states, in the second sentence, "Sample sets of less than 20 data points may be used only with the approval of the PTOB/PTPA." The commentor needs to develop and present an option to A2LA and then work through any feedback until they have an acceptable procedure.