IJCA Vol 5 Issue 1 - Flipbook - Page 41
2026 | Volume 5, Issue 1
The International Journal of Conformity Assessment
essential to define and document the intended
purpose of each comparison activity. While nonPT ILCs may provide valuable technical insight
and support internal quality assurance, they do not
replace proficiency testing requirements unless
their suitability is justified through a documented,
risk-based rationale.
3. Accreditation Requirements Governing
PT and ILC Participation
performance, and evaluation of measurements or
tests on the same or similar items by two or more
laboratories under predetermined conditions.
This broader definition encompasses a wide
range of comparison activities, many of which
serve purposes other than formal assessment of
laboratory competence.
The relationship between PT and ILC can therefore
be described as hierarchical: all proficiency
testing schemes are interlaboratory comparisons,
but not all interlaboratory comparisons qualify
as proficiency testing. Proficiency testing
is distinguished by predefined performance
criteria, formal evaluation mechanisms, and
structured reporting of results. Other ILCs may
be exploratory, developmental, or collaborative
in nature and may not result in a classification of
participant performance.
From an accreditation perspective, this distinction
has practical consequences. Participation in
proficiency testing is treated by accreditation
bodies as direct evidence of technical
competence. Other interlaboratory comparisons
may support method development, validation, or
internal benchmarking, but do not automatically
satisfy accreditation requirements unless
performance evaluation and acceptance criteria
are clearly defined and documented.
Examples of non-PT interlaboratory comparisons
include collaborative studies for method
development, value assignment exercises for
reference materials, and key or supplementary
comparisons conducted among National
Metrology Institutes. In such cases, the primary
objective is often to establish reference values
or demonstrate equivalence among expert
laboratories rather than to assess individual
laboratory competence against predefined criteria.
For calibration laboratories, it is therefore
Accreditation requirements governing proficiency
testing and interlaboratory comparison
participation are defined through a combination
of international standards and accreditation
body policies. ISO/IEC 17025 establishes general
principles related to monitoring the validity of
results, while ILAC policies provide additional
clarification on how these principles are to be
applied and assessed in practice. Together, these
documents form the framework within which
calibration laboratories plan, implement, and
evaluate PT and ILC activities.
Understanding the respective roles of ISO/IEC
17025 and ILAC-P9 is essential for interpreting
accreditation expectations. While ISO/IEC 17025
emphasizes flexibility and outcome-based
compliance, ILAC-P9 introduces more explicit,
risk-based requirements intended to ensure
consistent application across accreditation
bodies. The following sections outline these
requirements and their implications for calibration
laboratories.
3.1 ISO/IEC 17025:2017 — General Requirements
ISO/IEC 17025:2017 establishes the foundational
requirement for laboratories to monitor the validity
of their results through comparison with other
laboratories when such activities are available and
appropriate. Clause 7.7.2 identifies participation
in proficiency testing as one possible means
of fulfilling this requirement, while allowing
flexibility in how laboratories demonstrate ongoing
confidence in their results.
This principle-based approach recognizes that
suitable proficiency testing schemes may not be
available for all calibration activities. However,
ISO/IEC 17025 places clear responsibility on
laboratories to evaluate the outcomes of any
comparison activities undertaken. Clause 7.7.3
requires that results from proficiency testing or
interlaboratory comparisons be reviewed and that
corrective actions be initiated when performance
is unsatisfactory.
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