How to Plan and Structure an Interlaboratory Comparison

So you know that ISO/IEC 17025 interlaboratory comparison is a requirement—and now you’re ready to actually do one. Great! But how do you plan and structure it in a way that’s useful, efficient, and aligned with the standard?

The good news is, interlaboratory comparisons don’t have to be complicated. With a little planning and cooperation, they can become a regular part of your quality system. Whether you’re participating in an external program or organizing a comparison with another lab directly, the basic structure stays the same.

Here’s how to approach it:

1. Choose the Right Partner(s)

You’ll want to work with laboratories that:

• Use similar methods or instrumentation

• Work within the same measurement range

• Are accredited or have a known level of technical competence

For ISO/IEC 17025 interlaboratory comparison, compatibility matters. If the methods or scopes differ too much, comparing results might not be meaningful.

2. Agree on the Details

Before testing starts, both labs should agree on:

• The measurement or testing method to be used

• The sample type and how it will be handled

• The schedule for testing and reporting

• The performance criteria and what’s considered acceptable agreement

Clear communication upfront ensures that the ISO/IEC 17025 interlaboratory comparison delivers usable results—and avoids confusion later.

3. Document the Plan

Even if the comparison is informal or arranged between two labs, it still needs to be documented. This includes:

• The objective of the comparison

• Roles and responsibilities

• How the data will be evaluated

• What will happen if results differ significantly

A solid plan shows auditors that your ISO/IEC 17025 interlaboratory comparison isn’t just a checkbox—it’s part of a real, functioning system.

4. Keep It Realistic

Not every comparison needs to be large-scale. You can keep it simple by selecting one or two key parameters that are critical to your scope. What matters most is that the exercise gives you insight into the consistency and accuracy of your lab’s results.

By planning carefully and documenting clearly, you’ll turn ISO/IEC 17025 interlaboratory comparison into something that works for your lab—not just something you do for accreditation.

Next, we’ll explore how to interpret the results of a comparison—and what to do when things don’t line up as expected. Let’s keep going!

Analyzing and Interpreting Comparison Results

Once your ISO/IEC 17025 interlaboratory comparison is complete and the data is in, it’s time for the important part—making sense of the results. This is where you find out how your lab’s performance stacks up and whether any issues need to be addressed.

The goal here isn’t just to look for matching numbers. It’s about evaluating agreement, spotting outliers, and understanding what the data is really telling you. ISO/IEC 17025 expects labs to go beyond participation—it’s about using the results to drive real quality improvement.

What Should You Look For?

Start by reviewing the results alongside your comparison partner(s). You’ll want to look at:

• The degree of agreement between labs

• Any trends or biases (e.g., one lab consistently reading higher or lower)

• Whether the results fall within the pre-agreed limits or tolerances

For formal evaluations, you might see terms like z-scores or En values used to assess statistical agreement. Don’t worry if those sound intimidating—these just help show how close your result is to the average or expected value.

In an ISO/IEC 17025 interlaboratory comparison, a z-score close to zero generally means your result agrees well with the others. A high z-score (either positive or negative) may signal a problem that needs investigation.

What If There’s a Discrepancy?

If your lab’s result is outside the expected range, don’t panic. This is exactly why we do interlaboratory comparisons in the first place—to catch issues early and learn from them.

Ask questions like:

• Was the method followed correctly?

• Could there have been a sample handling error?

• Was the equipment in proper working order at the time?

Then document your findings and take corrective action if needed. And here’s the key: make sure you follow up. ISO/IEC 17025 doesn’t just expect you to identify the issue—it expects you to resolve it and make sure it doesn’t happen again.

What If Everything Looks Good?

That’s great news! It confirms your methods, equipment, and people are all working as intended. Still, don’t just file the results away. Use them to reinforce internal confidence, support training, or demonstrate competence during assessments.

Ultimately, analyzing results is where the value of an ISO/IEC 17025 interlaboratory comparison really shines. You’re not just comparing numbers—you’re gaining insight, improving processes, and proving that your lab produces dependable results.

Next, we’ll dive into how to document your findings and respond effectively within your quality management system. Let’s continue!

Documenting and Responding to Outcomes

Once you’ve analyzed the results of your ISO/IEC 17025 interlaboratory comparison, the next step is making sure everything is properly documented and, if needed, addressed. This part might not be the most exciting, but it’s absolutely essential—and it’s something auditors pay very close attention to.

Remember, ISO/IEC 17025 doesn’t just want to see that you participated in a comparison. It wants to see that you took the results seriously, learned from them, and integrated what you found into your quality management system.

Keep a Clear Record

Every ISO/IEC 17025 interlaboratory comparison should result in a full set of documented records. These don’t have to be overly complicated, but they should be complete and organized. Here’s what you should include:

• The plan or scope of the comparison

• Raw results and any statistical evaluations (like z-scores or En values)

• Notes on methods used and any deviations from agreed procedures

• Final evaluations and whether your lab’s results were satisfactory

• A summary of discussions or actions taken (especially if results didn’t align)

Having these details readily available not only helps you track performance over time—it shows external auditors that your lab takes its obligations under ISO/IEC 17025 interlaboratory comparison seriously.

Address Any Issues Promptly

If your results weren’t in line with expectations, don’t wait to take action. Investigate what happened and document the entire process—from the initial finding to the final resolution. This is your chance to demonstrate the effectiveness of your corrective action process.

Ask yourself:

• Was it a one-time issue or part of a bigger trend?

• Do staff need more training?

• Does the procedure or equipment need review or adjustment?

ISO/IEC 17025 is all about continual improvement, and your response to an ISO/IEC 17025 interlaboratory comparison is a direct reflection of how well your quality system is working.

Use the Outcome to Strengthen Your System

Even when everything goes smoothly, don’t miss the opportunity to use the results for improvement. You can:

• Share outcomes during team meetings or management reviews

• Use them to support decisions about methods or equipment

• Include them as evidence of competence during audits or customer assessments

In short, how you respond to the results of an ISO/IEC 17025 interlaboratory comparison is just as important as participating in the comparison itself. It’s where your lab can show maturity, transparency, and a true commitment to quality.

Next, we’ll look at how to make interlaboratory comparison a regular, integrated part of your lab’s quality routine—not just an occasional activity. Let’s wrap it all into daily practice.

Integrating Interlaboratory Comparison into Routine Practice

By now, you’ve probably realized that ISO/IEC 17025 interlaboratory comparison isn’t something that should sit on the sidelines. It’s not just an occasional checkbox for audits—it’s a key piece of your lab’s ongoing quality strategy. When done regularly and thoughtfully, it becomes part of your lab’s culture of accuracy and accountability.

So how do you make it part of your everyday operations without it feeling like a burden? The key is to treat it as routine, not reactive.

Make a Comparison Schedule

Just like you schedule equipment calibrations or internal audits, plan your ISO/IEC 17025 interlaboratory comparison activities. This might mean:

• Participating in one formal comparison each year

• Organizing informal comparisons with a peer lab every quarter

• Rotating through different parameters over time

When you schedule it in advance, it becomes a natural part of your quality cycle—not something you scramble to complete last minute before an audit.

Link It to Your Quality Objectives

Your quality management system should already have goals around consistency, reliability, and continuous improvement. ISO/IEC 17025 interlaboratory comparison fits right into those goals. Use the outcomes to:

• Track improvement in results over time

• Identify areas for training or procedural refinement

• Support decisions about method changes or new equipment

Treat the data you get as valuable feedback—because it is.

Involve the Whole Team

Interlaboratory comparisons aren’t just for managers or quality officers. Get your technicians, analysts, and support staff involved in planning, execution, and review. When your whole team understands the value of ISO/IEC 17025 interlaboratory comparison, they’re more likely to see it as a useful tool—not just an extra task.

You can even use it as part of training for new employees or as a way to test consistency between shifts or locations. The more you integrate it into your lab’s mindset, the more useful it becomes.

Document as You Go

Finally, keep things organized. Have a standard format or checklist for documenting each ISO/IEC 17025 interlaboratory comparison. That way, you don’t have to reinvent the wheel each time—and your documentation will be audit-ready with minimal stress.

The more naturally interlaboratory comparisons fit into your regular workflow, the more insights they’ll offer—and the easier it will be to maintain your lab’s technical credibility and accreditation status.

Let’s now pull everything together with a big-picture look at why this all matters for your lab’s long-term performance and reputation.

Why ISO/IEC 17025 Interlaboratory Comparison Matters Long-Term

When you zoom out and look at the bigger picture, it’s clear that ISO/IEC 17025 interlaboratory comparison is more than a technical exercise. It’s a long-term investment in your lab’s credibility, competence, and confidence.

Each time your lab participates in a comparison, you’re gathering proof—proof that your results are valid, your methods are sound, and your team knows exactly what it’s doing. That kind of evidence speaks volumes, not just to accreditation bodies, but also to customers, regulators, and internal stakeholders.

Regular ISO/IEC 17025 interlaboratory comparison helps you:

• Confirm the consistency and reliability of your results

• Catch hidden issues early, before they impact clients

• Continuously improve your measurement process

• Strengthen your audit readiness with traceable, objective data

• Build trust with external partners who rely on your accuracy

It also helps shift your lab’s mindset. Instead of focusing on just meeting the standard, your team starts aiming to exceed it—using every comparison as a learning opportunity, not a pass/fail test.

And here’s the best part: when ISO/IEC 17025 interlaboratory comparison becomes routine, it feels less like a chore and more like an essential quality tool. It becomes something your team values, because they see the real-world impact—better data, stronger systems, and a lab that’s recognized for doing things right.

So whether you’re just starting your first comparison or refining your process after years of participation, remember that it’s not about being perfect. It’s about staying consistent, curious, and committed to producing results you—and your clients—can trust.

Levy M.

I hold a Master’s degree in Quality Management, and I’ve built my career specializing in the ISO/IEC 17000 series standards, including ISO/IEC 17025, ISO 15189, ISO/IEC 17020, and ISO/IEC 17065.

My background includes hands-on experience in accreditation preparation, documentation development, and internal auditing for laboratories and certification bodies.

I’ve worked closely with teams in testing, calibration, inspection, and medical laboratories, helping them achieve and maintain compliance with international accreditation requirements.

I’ve also received professional training in internal audits for ISO/IEC 17025 and ISO 15189, with practical involvement in managing nonconformities, improving quality systems, and aligning operations with standard requirements.

At QSE Academy, I contribute technical content that turns complex accreditation standards into practical, step-by-step guidance for labs and assessors around the world.

I’m passionate about supporting quality-driven organizations and making the path to accreditation clear, structured, and achievable.