Last Updated on September 25, 2025 by Melissa Lazaro

ISO/IEC 17043 Alignment with ILAC P10 and Accreditation Bodies

Let’s be real—most PT providers know ISO/IEC 17043 inside and out. But when the topic of ILAC P10 comes up, things get fuzzy. Is it required? How does it relate to traceability? Are auditors even checking for it?

Here’s what I’ve seen: PT providers who understand how ISO/IEC 17043 and ILAC P10 fit together walk into audits with confidence. Others? They end up scrambling to justify reference values or explain subcontracting choices.

In this article, we’ll break it all down—what ILAC P10 is, how it links to ISO/IEC 17043, what accreditation bodies expect, and how you can align smoothly without overcomplicating your process.

What ISO/IEC 17043:2023 Is Really About—In Plain Terms

Before we talk about alignment, let’s revisit what ISO/IEC 17043:2023 asks of PT providers.

This standard is all about making sure that proficiency testing schemes are valid, fair, and well run. That means the design is solid, the evaluation makes sense, and the whole process builds trust in the results.

Some core things ISO/IEC 17043 covers:

• Designing PT schemes with clarity and technical soundness
• Assigning values participants can trust
• Protecting confidentiality
• Being impartial and consistent
• Following through with scheme reviews and improvements

In the 2023 revision, there’s more emphasis on risk-based thinking, impartiality, and traceability—which brings us straight to ILAC P10.

What Is ILAC P10, and Why Should You Care?

ILAC P10 is a policy document from ILAC (International Laboratory Accreditation Cooperation). Its full name is:
“ILAC Policy on the Traceability of Measurement Results”.

Now, that might sound like it only applies to calibration labs—but in reality, it applies to all conformity assessment bodies, including PT providers. If your scheme includes any measurement values—assigned values, reference points, expected results—then ILAC wants to know how those values are traceable to a known standard.

Here’s the core idea:
You can’t just say “this is the correct value.” You have to be able to show how that value is derived, and whether it’s traceable to an internationally accepted system—like the SI units, certified reference materials (CRMs), or accredited calibration labs.

And guess what? ISO/IEC 17043 also requires that you define how your assigned values are established. That’s where the two documents start to align naturally.

How ISO/IEC 17043 Aligns with ILAC P10—Section by Section

Let’s walk through a few areas where these two expectations connect directly.

Assigned Values and Traceability

ISO/IEC 17043 says you must assign values based on valid methods. ILAC P10 says those values must be traceable. That means:

• Using CRMs when possible
• Calibrating instruments through ISO/IEC 17025-accredited labs
• Documenting how the assigned value links back to the SI (or to a recognized reference)

If the traceability chain is unclear—or missing—you’re out of alignment.

Evaluation and Scoring

Both standards emphasize that performance evaluation must be:

• Based on consistent, statistical methods
• Justified with transparent rationale
• Linked to measurable, traceable benchmarks

This is where En scores, z-scores, and other metrics come in—but only if they’re properly grounded in reference data.

Subcontracting and Supplier Use

ISO/IEC 17043 requires oversight of any subcontracted services. ILAC P10 goes further by saying:

• If you use a calibration service, it should be accredited
• If it’s not accredited, you need a clear, documented justification

This means PT providers should maintain a supplier evaluation process—something many forget until audit time.

Risk-Based Thinking and Decision Rules

The 2023 version of ISO/IEC 17043 encourages providers to:

• Assess risks related to technical validity, traceability, impartiality
• Build risk registers and include traceability gaps
• Justify any non-traceable assigned values with supporting rationale

ILAC P10 supports this mindset. It’s not about perfection—it’s about transparency and justification.

What Accreditation Bodies Are Actually Looking For

This is where things get practical.

When your PT scheme is up for assessment, here’s what auditors often check:

• Can you demonstrate traceability of your assigned values?
• Have you documented the source of each reference value—CRM, standard method, or measurement?
• If using internal expertise, is it backed by validated data or comparison studies?
• Did you evaluate and document your calibration subcontractors (and are they accredited)?
• Do your evaluation methods (z-scores, En, pass/fail) make statistical sense based on the data you’ve got?

They’re not looking for perfection—but they are looking for intentional design and traceable decision-making.

Pro Tips for Aligning Without the Headache

Pro Tip 1: Build a “Traceability Justification File”

For every PT scheme you run, keep a file that includes:

• How the assigned value was set
• What reference materials or calibrations were used
• Certificates, CRM datasheets, or method validation documents
• A short paragraph explaining the traceability path

It makes audit time much smoother.

Pro Tip 2: If you use non-accredited suppliers, document why

Sometimes there’s no accredited provider for a very specific calibration or test. That’s okay—if you’ve evaluated them and recorded why you chose them.

Pro Tip 3: Include ILAC P10 in your internal training

Make sure your staff understands that traceability isn’t just a lab thing—it affects PT providers too. A quick 1-hour training can prevent a dozen audit headaches.

Pro Tip 4: Add traceability checkpoints to your risk register

Each PT scheme should include a mini risk review that answers:

• Are assigned values traceable?
• Are we relying on internal expertise too heavily?
• Do we have proof that our instruments were calibrated properly?

Common Mistakes PT Providers Make with Traceability

• Saying “we used a known value” without explaining how it was known
• Assuming a CRM is automatically valid without checking expiration or suitability
• Forgetting to assess subcontracted labs for accreditation
• Mixing up method validation with traceability of results
• Waiting for the auditor to ask—rather than building traceability into the scheme

FAQs – Because Everyone Asks These

Is ILAC P10 mandatory for ISO/IEC 17043 accreditation?
Not directly. But most accreditation bodies reference ILAC P10 as mandatory policy—so if you want international recognition, yes, it applies.

What if no certified reference or SI traceability exists?
You’re allowed to use expert-derived values or consensus—but you must justify the approach, explain the limitations, and document everything.

How much documentation is enough?
Enough to explain your thinking clearly to a trained assessor. If they can’t follow the traceability trail, it’s not enough.

Can I use my own lab’s measurements as the assigned value?
Yes—but only if the method is validated, the measurements are traceable, and you explain how you controlled bias.

It’s About Confidence, Not Just Compliance

Let’s wrap this up simply.

ISO/IEC 17043 gives you the structure to run technically sound PT schemes. ILAC P10 reinforces one key piece of that structure: traceability. Together, they ensure that when you assign a value in a PT scheme, that value means something—and everyone involved can trust it.

If you align with both standards, you’re not just passing audits. You’re building better schemes, earning recognition faster, and providing labs with tools they can rely on to prove their own competence.

Need help reviewing your traceability files, PT documentation, or risk registers?
That’s what we do. We help PT providers align with confidence—before the auditor shows up.