IJCA Vol 5 Issue 1 - Flipbook - Page 43
2026 | Volume 5, Issue 1
The International Journal of Conformity Assessment
related to impartiality and consistency in PT
provision. PT providers must demonstrate that
evaluation methods are applied objectively
and without bias, reinforcing confidence in the
technical validity of PT outcomes. However,
accreditation of the PT provider does not transfer
responsibility to the participant laboratory.
Calibration laboratories remain responsible for
understanding how results were evaluated and
for determining whether the evaluation methods
are appropriate for their scope and claimed
measurement uncertainties.
and operational factors such as measurement
complexity, uncertainty levels, historical
performance, stability of reference standards,
personnel changes, and potential impact on
customers or regulators.
In practice, this requires laboratories to review
PT documentation critically and to assess the
suitability of evaluation methods, particularly in
calibration contexts where uncertainty plays a
central role. Where PT schemes apply evaluation
approaches that do not adequately account for
measurement uncertainty, laboratories may need
to document their assessment and consider
supplementary or alternative comparison activities.
The PT/ILC participation plan must define how
the laboratory intends to address its entire
accredited scope over the accreditation cycle.
At a minimum, the plan should identify technical
disciplines covered, the type of comparison
activity selected, participation frequency, and the
technical justification for each decision. It should
also describe actions to be taken in response to
unsatisfactory results, including investigation,
corrective action, and verification of effectiveness.
5. Risk-Based Planning for PT and ILC
Participation
Recent revisions to ILAC-P9 emphasize
that participation in proficiency testing and
interlaboratory comparisons must be planned
strategically rather than approached as isolated
or periodic activities. For calibration laboratories,
this represents a transition toward structured,
risk-based planning integrated into the quality
management system.
ILAC-P9 requires laboratories to establish and
maintain a documented PT/ILC participation plan
covering the full accredited scope. The purpose of
this plan is not only to demonstrate compliance,
but to provide a technically justified framework
for selecting comparison activities, defining
participation frequency, and ensuring that results
are used effectively to support confidence in
measurement results.
5.1 Mandatory Participation and Risk Assessment
Participation in PT or suitable ILCs is mandatory
when such activities are available, appropriate,
and necessary. Laboratories must conduct a
documented risk assessment to justify decisions
regarding participation strategy, including activity
selection and frequency.
This approach aligns with the risk-based thinking
introduced in ISO/IEC 17025:2017. Rather
than applying uniform participation intervals,
laboratories are expected to consider technical
By linking participation decisions to risk, ILAC-P9
encourages laboratories to focus resources where
the consequences of measurement error are
greatest, while maintaining appropriate coverage
of the accredited scope.
5.2 Documented PT/ILC Participation Plans
The plan is intended to function as a living
document within the quality management system.
It should be reviewed periodically, typically as
part of management review, and updated to
reflect changes in scope, measurement capability,
equipment, personnel, or external requirements.
5.3 Availability, Appropriateness, and Scope
Coverage
ILAC-P9 draws a clear distinction between
availability and appropriateness of PT schemes.
Availability refers to whether a scheme exists
and is accessible, while appropriateness requires
technical alignment with the laboratory’s scope,
uncertainty levels, and measurement methods.
When formal PT schemes are unavailable or
inappropriate, laboratories may rely on alternative
interlaboratory comparisons, provided that their
selection is justified and documented. Searches
for available schemes, technical justification
for alternatives, and periodic reassessment are
essential elements of this process.
For laboratories with broad scopes, risk-based
planning should ensure representative coverage
of all significant technical disciplines over
time. Grouping of activities may be used where
equivalence can be demonstrated, but this
approach must be documented and defensible.
Failure to demonstrate adequate scope coverage
may raise concerns during accreditation
assessments, regardless of individual comparison
outcomes.
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