IJCA Vol 5 Issue 1 - Flipbook - Page 40
The International Journal of Conformity Assessment
2026 | Volume 5, Issue 1
Pro昀椀ciency Testing and Interlaboratory Comparisons in
Calibration Laboratories:
Implications of ISO/IEC 17043:2023 and ILAC-P9:01/2024
By Giulia Suriani, Program Manager, Calibration Laboratory Accreditation Program, International
Accreditation Service, Inc. (IAS)
GENERAL INFORMATION
DOI: 10.55459/IJCA/v5i1/GS
Keywords: Pro昀椀ciency testing; interlaboratory
comparison; calibration laboratories; ISO/IEC 17043;
ILAC-P9; ISO/IEC 17025; measurement uncertainty
ABSTRACT
Proficiency testing (PT) and interlaboratory
comparisons (ILC) are essential tools for
demonstrating and maintaining technical
competence in accredited calibration laboratories.
Recent revisions to ISO/IEC 17043:2023 and
ILAC-P9:01/2024 introduce more explicit and riskbased expectations for PT and ILC participation,
evaluation, and documentation. This article
clarifies the distinction between proficiency
testing and other forms of interlaboratory
comparison, outlines applicable accreditation
requirements, and examines implications for
participation planning, performance evaluation,
and continual improvement. Particular attention
is given to the suitability of statistical evaluation
methods in calibration contexts, including the use
of En values, and to the integration of PT and ILC
outcomes into laboratory quality management
systems to support confidence in measurement
results.
1. Introduction
Proficiency testing and interlaboratory
comparisons are widely used to support
confidence in measurement results and to
demonstrate technical competence in accredited
calibration laboratories. Through comparison with
other laboratories, PT and ILC activities provide
external evidence that measurement processes,
uncertainty estimates, and technical practices are
performing as intended.
Recent revisions to ISO/IEC 17043:2023 and
ILAC-P9:01/2024 have significantly strengthened
expectations related to PT and ILC participation.
These updates introduce more explicit
requirements for risk-based planning, documented
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justification, and evaluation of results across
the accredited scope. As a result, calibration
laboratories are expected not only to participate
in appropriate comparison activities, but also to
demonstrate informed selection, interpretation,
and effective use of outcomes within their quality
management systems.
This article examines the implications of these
developments for calibration laboratories. It
clarifies the distinction between proficiency
testing and other forms of interlaboratory
comparison, outlines relevant accreditation
requirements, and discusses considerations
related to participation planning, performance
evaluation, and continual improvement. By
situating PT and ILC participation within a riskbased conformity assessment framework, the
article aims to support laboratories in meeting
evolving accreditation expectations while
strengthening confidence in measurement results.
2. De昀椀nitions and Scope: Pro昀椀ciency
Testing and Interlaboratory Comparisons
Recent revisions to international standards and
accreditation policies have renewed focus on
the distinction between proficiency testing (PT)
and other forms of interlaboratory comparison
(ILC). Although the terms are sometimes used
interchangeably in practice, their differentiation
is essential for accreditation purposes and for
demonstrating technical competence.
ISO/IEC 17043:2023 defines proficiency testing
as the evaluation of participant performance
against pre-established criteria by means of
interlaboratory comparisons. This definition
makes clear that PT is characterized not only
by participation in a comparison exercise, but
by the formal evaluation of results against
defined acceptance criteria. Participation in
an interlaboratory comparison alone does not
constitute proficiency testing unless performance
evaluation is an explicit component of the scheme.
In contrast, ISO/IEC 17043:2023 defines an
interlaboratory comparison as the design,
