An analyst is trained on a new method, step by step, until they are working independently and doing it well. The training record gets signed off. On paper, everything looks exactly as it should.

The Quality Manager still has that analyst perform the lab’s next proficiency testing (PT) round for that parameter. A training record shows someone was taught correctly. A PT result shows something different: whether that training holds up in practice, checked by an outside expert who has no stake in the outcome.

What does ISO/IEC 17025:2017 ask for

That distinction has a name in the standard. Clause 6.2.6 is what makes an Authorised Signatory an Authorised Signatory: a laboratory must specifically authorise someone before they can review results or sign a report in their own name. A signature is a claim — “I stand behind this” — and the clause asks what backs it. Backing it up on paper is Clause 6.2.5’s job: a documented procedure and records covering how that authorisation was actually reached, not just that it was.

Clause 6.2.3 raises the bar higher still: competence means recognising when a result has drifted from where it should be, not just running a method correctly. A training record proves someone attended a programme. Whether they can catch a result quietly going wrong, on their own, months later, is the harder question — and it is the one a PT round is actually built to answer.

Where proficiency testing fits

This is exactly the gap proficiency testing closes. PT is treated as a routine sample, worked into a lab’s normal testing schedule alongside everything else on the bench. Because of that, the result that comes back is a genuine record of how a person performs their actual, everyday work.

Round after round, that record becomes something concrete an Authorised Signatory can point to: not a memory of having done well once, but a documented history of results holding up over time.

What backs the signature

When the assessor asks the question, the Authorised Signatory has something real to answer with.

“Here is my own PT performance record, across these rounds, for these parameters.”

That is evidence sitting in the room, ready to be examined.

One tool among several

Proficiency testing does not stand in isolation from a lab’s other checks. ISO/IEC 17025:2017, Clause 7.7.1 sets out a broader toolkit for monitoring the validity of results, including reference materials, control charts, intermediate checks on equipment, and repeat testing. Clause 7.7.2 then adds a further requirement: comparing a laboratory’s performance against other laboratories, through proficiency testing or interlaboratory comparisons other than proficiency testing.

From training to renewed confidence

A tool for training, too

PT results carry value that reaches beyond the authorisation decision itself. Every round produces a precise picture of where an analyst’s skills genuinely stand: which methods are solid, and which specific step in a procedure could use reinforcement, whenever that need shows up.

Used this way, PT becomes a training evaluation tool as much as an authorisation tool. A lab reviewing its PT results across a full team gets a precise map of where to focus: a specific method one analyst should practise further, or a pattern repeating across several analysts that points toward a shared training gap rather than an individual one. That level of precision is hard to reach from a general training calendar built on assumptions about what people probably need.

From a snapshot to a trend

Competence shifts over time. Methods change, and a skill that goes unused for a while can fade, quietly, without anyone noticing. A single PT round is a snapshot — a lagging read on how someone performed once. A lab that tracks results across several rounds gets something more useful: a trend line, a read on whether a person’s competence is climbing, holding steady, or slipping, well before that slide shows up as a wrong result on a real sample.

This is risk-based thinking applied to personnel competence, not just to methods or equipment: a trend spotted early is a risk addressed before it becomes a nonconformity, rather than an outcome explained after the fact.

The stakes reach further than the lab itself. Every test report a lab issues gets trusted by someone who never sees the testing happen: the regulator approving a shipment, the consumer buying a product tested against a standard, the customer relying on a certificate of analysis to make a decision. Personnel competence evidence is not only an audit requirement — it is part of what keeps that entire chain of trust intact, from the bench to the shelf.

That, ultimately, is what proficiency testing does for personnel evaluation: it turns a judgment call into something documented, an assumption into something checkable, and a signature into something backed by evidence.