Last Updated on December 23, 2025 by Melissa Lazaro

Understanding ISO/IEC 17043 Without the Confusion

If you work anywhere near laboratory accreditation, proficiency testing eventually comes up.
And when it does, ISO/IEC 17043 usually follows—often with a lot of uncertainty.

In my experience working with proficiency-testing providers and accreditation assessments, the standard itself isn’t the real problem.
The confusion is.

ISO/IEC 17043 is often misunderstood, underestimated, or mixed up with laboratory standards like ISO/IEC 17025. That misunderstanding leads to wrong accreditation choices, delayed applications, and unnecessary audit findings.

This article explains ISO/IEC 17043 clearly and practically:

• What the standard actually is
• Why it exists
• Who it applies to
• Why it matters in the accreditation ecosystem

By the end, you should be able to explain ISO/IEC 17043 confidently—to an auditor, a regulator, or your own team.

What ISO/IEC 17043 Is: A Plain-English Explanation

ISO/IEC 17043 is the international standard for proficiency-testing providers.

It defines how organizations must design, operate, and evaluate proficiency-testing (PT) schemes and interlaboratory comparisons when those activities are used to assess laboratory performance.

Put simply:

• Laboratories generate test results
• Proficiency-testing providers evaluate how well those laboratories perform

ISO/IEC 17043 exists to make sure that evaluation process is fair, technically sound, and trustworthy.

The standard covers activities such as:

• Designing PT schemes
• Preparing and distributing test items
• Applying statistical evaluation methods
• Reporting performance results
• Protecting participant confidentiality

It does not assess laboratory testing competence.
It assesses the competence of the organization evaluating laboratories.

That distinction is critical.

Why ISO/IEC 17043 Matters in the Accreditation Ecosystem

Proficiency testing plays a central role in laboratory accreditation.
Accreditation bodies rely on PT results to judge whether laboratories are competent.

That creates a chain of trust:

• Laboratories trust PT providers
• Accreditation bodies trust PT results
• Regulators and end users trust accredited labs

ISO/IEC 17043 is what holds that chain together.

Without it, PT results become harder to defend.
Statistical methods get questioned.
Impartiality gets challenged.

I’ve seen situations where technically sound PT schemes lost credibility simply because there was no clear ISO/IEC 17043 framework behind them. Once trust erodes, it’s difficult to rebuild.

This is why accreditation bodies increasingly expect PT schemes to align with ISO/IEC 17043—even when it isn’t explicitly stated at the start.

Who ISO/IEC 17043 Applies To (and Who It Doesn’t)

ISO/IEC 17043 applies based on activities, not titles.

It clearly applies to organizations that:

• Design and operate proficiency-testing schemes
• Organize interlaboratory comparisons for external participants
• Evaluate laboratory performance and issue conclusions

This includes:

• Commercial PT providers
• Industry or sector-specific scheme operators
• Independent ILC organizers

It does not usually apply to:

• Laboratories that only participate in PT
• Internal quality-control comparisons used solely for learning
• Organizations that share data informally without evaluation

A useful rule of thumb is simple:
If external parties rely on your evaluation to judge laboratory competence, ISO/IEC 17043 likely applies.

ISO/IEC 17043 vs ISO/IEC 17025: Understanding the Difference

ISO/IEC 17043 and ISO/IEC 17025 often appear together, but they serve different purposes.

ISO/IEC 17025 focuses on:

• Producing technically valid test or calibration results
• Method validation
• Measurement uncertainty
• Traceability

ISO/IEC 17043 focuses on:

• Evaluating laboratory performance
• Statistical assessment
• Scheme design and impartiality

One does not replace the other.

An organization may need:

• ISO/IEC 17025 if it performs testing or calibration
• ISO/IEC 17043 if it evaluates laboratories
• Both, if it does both activities

Assessors are very clear about this distinction during audits.

What ISO/IEC 17043 Requires at a High Level

ISO/IEC 17043 is structured around a few core themes.

At a high level, it requires PT providers to demonstrate:

• Impartiality and confidentiality
  Decisions must be unbiased, and participant data must be protected.
• Competence
  Staff must have the technical and statistical skills needed for their roles.
• PT scheme design and planning
  Schemes must be valid, consistent, and defensible.
• Statistical evaluation
  Performance criteria must be appropriate and justified.
• Management-system controls
  Activities must be planned, monitored, reviewed, and improved.

Assessors tend to focus heavily on scheme design and statistics, because that’s where weak PT schemes usually fail.

Key Benefits of ISO/IEC 17043

ISO/IEC 17043 is often viewed as a compliance requirement, but its value goes beyond that.

When implemented properly, it:

• Improves credibility and trust in PT results
• Increases acceptance by accreditation bodies and regulators
• Reduces disputes and challenges from participants
• Strengthens internal consistency and control
• Supports scalability as PT activities grow

For many providers, these benefits only become obvious after operating without the standard and encountering avoidable problems.

Common Misunderstandings About ISO/IEC 17043

Several persistent misconceptions create risk for organizations.

Some believe:

• ISO/IEC 17043 is only for large providers
• ISO/IEC 17025 is sufficient for PT activities
• Accreditation can wait until clients demand it

These assumptions often delay proper implementation.
When ISO/IEC 17043 eventually becomes unavoidable, timelines are tighter and pressure is higher.

Clear understanding early on avoids that cycle.

How ISO/IEC 17043 Fits Into an Implementation Journey

Organizations typically approach ISO/IEC 17043 in stages.

It usually starts with:

• Clarifying which activities fall under the standard
• Mapping current practices against requirements
• Identifying gaps in competence, statistics, and controls

From there, documentation, training, and system refinement follow.

The earlier this clarity is achieved, the smoother the accreditation process tends to be.

FAQs: ISO/IEC 17043 Overview

What is ISO/IEC 17043 in simple terms?
It is the international standard that defines how proficiency-testing providers must operate to evaluate laboratory performance reliably and impartially.

Is ISO/IEC 17043 mandatory?
Not always by law, but often expected by accreditation bodies, regulators, and industry schemes.

How long does ISO/IEC 17043 accreditation take?
Timeframes vary, but preparation and assessment typically take several months, depending on scope and readiness.

Conclusion: Why ISO/IEC 17043 Truly Matters

ISO/IEC 17043 exists to protect confidence in laboratory competence.

It ensures that performance evaluations are fair, technically sound, and trusted.
It supports accreditation systems that rely on consistent and credible PT results.

When organizations understand ISO/IEC 17043 clearly, decisions become easier:

• Whether it applies
• How to implement it
• How to prepare for assessment

The most effective approach is proactive understanding, not reactive compliance.
That clarity is what turns ISO/IEC 17043 from a source of confusion into a practical, valuable standard.