Last Updated on September 25, 2025 by Melissa Lazaro

Why ISO/IEC 17043:2023 is Essential for Laboratories

Let’s get right to it—if you run or work in an ISO/IEC 17025-accredited laboratory, you’re already knee-deep in quality assurance. You’re monitoring results, reviewing equipment calibration, overseeing analyst competence, and keeping up with internal audits.

But here’s something I’ve seen time and again: many labs still treat proficiency testing (PT) like a checkbox. They sign up, do the tests, send in the data, and assume they’re covered. What they miss is that PT results are only as reliable as the provider behind them.

And that’s where ISO/IEC 17043:2023 comes in.

In this article, we’re going to talk about:

• Why this standard matters to you, even if you don’t offer PT schemes.
• How it impacts your ISO/IEC 17025 compliance.
• What can go wrong if you ignore it.
• And how to confidently evaluate your PT providers using 17043 as your guide.

You don’t need to become an expert in 17043 to benefit from it—but you do need to understand how it supports your lab’s credibility, consistency, and audit-readiness.

What Is ISO/IEC 17043:2023 Really About?

ISO/IEC 17043:2023 is the international standard for the competence of proficiency testing providers. It tells PT organizations how to properly plan, conduct, evaluate, and manage PT schemes.

In simpler terms? It’s the standard that makes sure the tests you’re using to verify your competence are being run competently themselves.

It covers things like:

• Statistical validity of the evaluation methods.
• Confidentiality of participant data.
• Fairness and impartiality in scheme design.
• The overall effectiveness of PT delivery and feedback.

Here’s the deal—if your lab participates in a PT scheme that isn’t following these principles, then even great results may not stand up to scrutiny during an audit.

Real-life example from my consulting work:

A well-equipped food testing lab was preparing for its ISO/IEC 17025 surveillance audit. They had clean records, strong internal QA, and a solid team. But their PT reports came from a provider that wasn’t ISO/IEC 17043-accredited—and worse, didn’t disclose how they calculated z-scores. The assessor flagged every PT round as unverifiable, and the lab had to redo three entire schemes with a recognized provider.

It wasn’t a failure in testing—it was a failure in selecting a credible PT partner.

Why Proficiency Testing Isn’t Just About Passing or Failing

Some labs think, “As long as we’re participating, we’re compliant.” That’s only half true.

ISO/IEC 17025 requires labs to ensure the validity of their results, and PT is one of the main tools used to do that. But participating in any PT scheme isn’t enough. You’re expected to:

• Evaluate the provider’s competence.
• Understand the evaluation method.
• Respond meaningfully to any unsatisfactory results.
• Maintain records that show your decision-making process.

ISO/IEC 17043 helps ensure that all these pieces—from sample design to result interpretation—are managed professionally and transparently by the PT provider.

This matters even more in specialized fields like microbiology, environmental testing, and calibration, where subtle variations in method or matrix can significantly impact your PT results.

So here’s the takeaway: proficiency testing isn’t just a metric—it’s a mirror. But that mirror is only useful if it isn’t cracked by poor scheme design or biased scoring.

How ISO/IEC 17043 and ISO/IEC 17025 Fit Together (and Why It Matters)

Let’s clarify this connection because it trips up a lot of labs.

ISO/IEC 17025 is about your lab’s operations—your competence, traceability, method validation, and internal controls. But it doesn’t operate in a vacuum. You rely on external PT providers to challenge and verify your performance.

ISO/IEC 17043 ensures that those providers are:

• Statistically competent.
• Logistically organized.
• Ethically managed.
• Impartial and transparent.

If you’re using PT data to back up your lab’s validity claims, then that data has to come from a provider who’s doing their part properly. That’s exactly what ISO/IEC 17043 guarantees.

Another field example:

A calibration lab specializing in pressure instruments participated in a PT round where they scored poorly. Upon investigation, it turned out the test items were damaged in transit, and the provider hadn’t followed up with verification. Since the provider wasn’t ISO/IEC 17043-accredited, there was no requirement for transparent complaints handling or corrective action. The lab took the hit—unfairly.

That wouldn’t have happened with a provider bound by 17043.

What Can Go Wrong When Labs Ignore ISO/IEC 17043?

Let’s be real—this is where the risks pile up.

When labs don’t pay attention to how their PT provider operates, they open themselves to:

• Accreditation problems – assessors may reject PT data if the provider’s credibility is unclear.
• Weak evidence for corrective action – if you can’t explain the evaluation method, it’s hard to defend or improve your lab’s performance.
• Loss of trust – clients and regulators may question your competence if PT results are from an unrecognized or unstructured scheme.
• Higher costs – if PT needs to be repeated (or supplemented), that’s more money and time lost.

From the field:

One global lab group ran internal PT schemes across five locations. But without following ISO/IEC 17043 principles, the program lacked impartiality safeguards. One location designed the schemes and interpreted results—without external review. During a corporate audit, this was flagged as a conflict of interest. The internal scheme was scrapped and had to be rebuilt under 17043-aligned principles.

They weren’t trying to cut corners—they just didn’t know better.

How Labs Can Use ISO/IEC 17043 to Choose Better PT Providers

So, what can your lab do right now?

Even if you’re not offering PT, you can use ISO/IEC 17043 as a tool to assess your providers. Here’s what to look for:

• Accreditation to ISO/IEC 17043 from a recognized body.
• A PT scheme that matches your lab’s specific test scope or matrix.
• Transparent statistical methods (z-scores, En values, etc.).
• Confidentiality clauses—your results should be protected.
• A mechanism for participant feedback and complaints handling.

Make it a standard operating practice to evaluate PT providers annually—just like you do for suppliers, subcontractors, and calibration services.

If they’re not accredited? That doesn’t automatically mean they’re incompetent—but you’ll need to do a documented review to justify using them.

Pro Tips for Labs That Want to Stay Ahead of the Game

Pro Tip 1: Check the accreditation scope, not just the certificate

Many labs see “ISO/IEC 17043-accredited” and stop there. But the scope matters. A provider may be accredited for microbiology but not for the heavy metals PT you need. Always match your tests to their accredited scope.

Pro Tip 2: Use ISO/IEC 17043 as a checklist during internal audits

Incorporate basic 17043 clauses into your annual internal audit. Ask questions like:

• How does our PT provider evaluate performance?
• Do we know their complaints process?
• What’s their track record of timely feedback?

Pro Tip 3: Keep a PT provider evaluation file

Store accreditation documents, past schemes, complaints (if any), and email correspondence. If an assessor asks how you picked your PT provider, you’ll have a ready answer with documented evidence.

Pro Tip 4: If using a non-accredited provider, assess and document the risks

Sometimes there’s no accredited provider available for your matrix. That’s fine—but create a short internal report showing:

• Why you chose this provider
• How you evaluated their competence
• What alternate QA measures you put in place (e.g. replicate testing, internal checks)

Common Mistakes Labs Make With PT (And How to Avoid Them)

Here are mistakes I’ve seen even strong labs make:

• Choosing PT providers based on cost or convenience—not credibility.
• Skimming PT reports and filing them away without evaluating the feedback.
• Assuming that good results = no further action.
• Failing to follow up or document actions taken after unsatisfactory scores.
• Ignoring trends in repeated PT rounds—like slight but consistent bias.

Avoiding these pitfalls doesn’t take much—it just takes awareness, ownership, and better systems.

FAQs: What Labs Need to Know About ISO/IEC 17043

Is ISO/IEC 17043 required for laboratories?
No, the standard is written for PT providers. But labs are expected to ensure the competence of the PT schemes they participate in, and ISO/IEC 17043 is the best way to do that.

Can I use a non-accredited PT provider?
Yes, but only with justification. Accreditation makes things easier, but not mandatory. You must document how you evaluated the provider’s competence and what risks you identified.

What if I’m running internal PT within our lab network?
Then ISO/IEC 17043 should be your design guide—even if you’re not pursuing formal accreditation. It’ll help you build fair, confidential, and statistically sound internal comparisons.

Why This Isn’t Just About Providers—It’s About You

At the end of the day, ISO/IEC 17043:2023 is a safety net for your lab’s reputation.

You work hard to produce reliable, defensible results. But if the PT data you rely on is flawed, that entire picture gets blurry. When you understand and apply ISO/IEC 17043—even as a participant—you’re making sure your evidence is credible, your audits are smoother, and your quality system is complete.

And if you ever decide to offer your own PT schemes in the future? You’re already ahead of the curve.

Need help reviewing your PT providers or building a 17043-aligned checklist? That’s what we do. Let’s build your confidence from the outside in—starting with the standards that shape your lab’s future.