IAS POLICY ON PROFICIENCY TESTING FOR LABORATORIESSCOPE:
This document defines the International Accreditation Service (IAS) policy on the use ofProficiency Testing (PT) for laboratory accreditation. Successful results from PT are anindication of a laboratory’s technical competence and are an essential part of IAS
accreditation. Proficiency testing is a tool used by laboratories and accreditation bodies formonitoring test and calibration results and for verifying the effectiveness of the accreditation
process. This policy incorporates the PT requirements outlined in ILAC-P9: 06/2014, ILAC
Policy for Participation in Proficiency Testing Activities.
REFERENCES:
ISO/IEC Standard 17025:2017, General requirements for the competence of testing andcalibration laboratories
ISO/IEC Standard 17043, Conformity assessment – General requirements for proficiency
testingILAC-P9: 06/2014, ILAC Policy for Participation in Proficiency Testing Activities
POLICY:In accordance with ILAC P9, IAS-accredited laboratories or laboratories seeking accreditation
are required to document a formal “PT Participation Plan (Plan).” This Plan is to be formulatedby the laboratory and should address the laboratory’s minimum level and frequency ofparticipation in PT activities and shall be regularly reviewed in response to changes in staffing,methodologies, instrumentation, etc. The Plan will be reviewed on-site by IAS assessors
during assessments.
Laboratories that are accredited or seeking accreditation to ISO/IEC Standard 17025:2017 areexpected to participate in at least one proficiency test (PT) for each field of accreditation where
the tests are (1) available, (2) appropriate, and (3) do not cause undue hardship for thelaboratory. The laboratory is expected to complete the PT(s) within four years.
In fields that contain multiple significant disciplines, at least one PT is expected for eachsignificant discipline, within four years as outlined above. An example is the field of calibration,
which has significant disciplines such as dimensional, mechanical, electrical, andRF/microwave.
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There may also be circumstances in which PT participation has been mandated for thepurposes of accreditation by regulatory bodies, industry or professional sector requirements ora Regional Cooperation Body.
PT is not a tool for determining calibration and measurement capability (CMC); PT is a tool thatis used to monitor laboratory performance with respect to other laboratories, and may be usedby the laboratory to identify appropriate improvements to laboratory processes.
ARTIFACTS:
Artifacts or items for testing or calibration generally are one of two types. They are either
characterized or non-characterized.
Characterized artifacts are typically an easily definable item. An example is a set of gauge
blocks. Characterized artifacts are sent to a laboratory that will act as a reference laboratory,
such as a National Measurement Institute (NMI). The values provided by the referencelaboratory become the reference value(s) for the artifact. Additional laboratories within the PT
run tests or calibrations, and their results are calculated relative to the reference value.
Non-characterized artifacts are not easily defined. An example would be concrete. The actual
strength value of the artifact will depend on such variables as the water, sand, and exact mix
ratios that are used. There is no reference laboratory for non-characterized artifacts, andtherefore no specific reference value for the artifact. Results from the test or calibration arecalculated relative to the results for other laboratories participating in the PT.
EVIDENCE:
Each laboratory is required to maintain a PT Participation Plan and evidence of its involvement
in PT activities. This evidence must include the testing results, including any observations andderived data, and clear identification of the laboratory.
The evidence must be in English, or translatable into English.
PARTICIPATION:
Both calibration and testing laboratories are expected to participate in PTs that demonstrate
their accredited capabilities. For calibration laboratories, it is important that the PT results
submitted reflect the level of capabilities claimed in the CMC, i.e., the uncertainties reportedwith PT results should be similar to those claimed in the scope of accreditation. Any significant
differences in uncertainties should be due to the artifact alone. The assessor team will assess
the appropriateness of the PT. Whenever possible, ISO/IEC 17043 accredited PT providers
should be used.
If the laboratory’s results are classified as “outliers,” the laboratory is expected to:•Internally document the outlier status using its own internal mechanism, such as aninternal audit discrepancy report.
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IAS Policy on Proficiency Testing•
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Investigate to determine the cause and likely effect(s) of the outlier.
Investigate to determine if the cause of the outlier may have affected any tests orcalibrations for customers, the extent of any effect, and whether the effects areacceptable or if a recall is necessary.
Develop and implement a plan as appropriate for corrective action, to address any
noted discrepancies, or for preventive action to improve laboratory processes.
Specifically document these steps, for each outlier result.
Review each outlier and the subsequent investigation: the review must be documented
in the minutes of the management review meeting.
The laboratory is strongly encouraged to directly relate any plan for corrective or
preventive action to business support processes (e.g., training, purchase of equipment,
procedure review/improvement).

Where a PT (1) is not available, (2) is not appropriate, or (3) would place an undue hardship ona laboratory, other forms of interlaboratory comparisons must be performed and results
analyzed. Any outliers must be treated in the same fashion as those arising from a PT.
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