ANALYTICAL PERFORMANCE
Method verification and validation in medical laboratories
Identify the evidence you need—and the limits of what a study can establish.
By Stephen MacDonald · Updated 30 September 2026
Start with the claim and the intended use
Verification checks whether specified requirements are met under the laboratory’s conditions. Validation establishes that the requirements and resulting performance are adequate for the intended use. The practical starting point is therefore the examination, the proposed use and the evidence already available. A familiar label such as “verification pack” does not establish that the selected experiments answer the right questions.
A commercially supplied method used within its stated scope may have substantial supporting evidence. The laboratory still needs to assess local implementation. A changed specimen type, altered procedure or use outside the established scope raises additional questions; a small repeat of the original precision study may not answer them. The exact work depends on the change, the evidence and applicable requirements. CLSI EP19 provides a framework for locating relevant evaluation guidance. [1]
Separate three questions
| Question | Why it matters |
|---|---|
| What has already been established? | Review the stated scope, claims, supporting evidence and limitations. |
| What must be demonstrated locally? | Identify conditions and characteristics that the existing evidence does not adequately cover. |
| What will support continued use? | Define the monitoring and review needed after implementation. |
A precision study is one part of the evidence
CLSI EP15 addresses verification of precision claims and estimation of bias. That scope should not be mistaken for a complete evaluation of every property of an examination. Detection capability, interference, measuring interval and other relevant characteristics need appropriate evidence of their own. [2]
Similarly, a comparison with another procedure addresses differences under the studied conditions. It does not establish that the comparator is a reference procedure, or that agreement at high concentrations establishes agreement near a decision threshold. CLSI EP09 addresses comparison and bias estimation using patient samples. [3]
Write the decision before collecting data
State the performance characteristic, concentration range, materials and relevant operating conditions. Specify the criterion, its source and the method of assessment. Decide how estimates close to a limit, missing observations, exclusions and inconclusive findings will be handled. The design should follow the claim; a convenient number of specimens is not a justification by itself.
Recognising the limits of a verification
A worked scope example
A fictional laboratory is preparing to introduce a concentration assay used around a low clinical decision threshold. Its initial study contains repeated measurements of a control material well above that threshold and patient specimens concentrated in the middle of the measuring interval.
Those data may provide useful information about precision and comparison in the regions studied. They do not, on their own, establish low-concentration performance or exclude specimen-specific interference. A conclusion covering the whole claimed application would exceed the evidence.
The appropriate response is to identify which claims remain unsupported and select suitable additional evidence. This could mean extending concentration coverage or evaluating a relevant characteristic separately. It does not mean automatically repeating every possible study. The study plan should explain why each activity is needed and what decision it will support.
Allow an inconclusive outcome
A performance estimate is not known without uncertainty. An estimate near an acceptance limit can leave the conclusion unresolved, depending on the planned decision rule and study design. A point estimate on the favourable side of the limit is not always sufficient evidence for acceptance. Conversely, a result requiring investigation should not be dismissed as method failure without considering the evidence and study conditions.
Retain exclusions and their reasons. If more data are required, explain why and how they will be collected and analysed. A sequence of undocumented repeats followed by reporting only the favourable result conceals the decision process.
Report the scope of the conclusion
A useful report identifies the method and intended use, the evidence considered, the design, the results, the criteria and the resulting conclusion. It also states what was not studied, unresolved limitations and any conditions attached to implementation. Readers should be able to distinguish a measured finding from the judgement made from it.
Connect implementation to routine evidence
Verification provides a starting record. Routine IQC, EQA, change control and review provide further evidence as use broadens over time. A reagent change, software change or newly recognised limitation should trigger consideration of what needs reassessment. A change does not automatically require complete revalidation, but its impact should be considered and documented.
Sources and further reading
- [1] CLSI EP19 — Framework for evaluating examination performance (public overview).
- [2] CLSI EP15 — Precision verification and bias estimation (public overview).
- [3] CLSI EP09 — Measurement procedure comparison and bias estimation using patient samples (public overview).
- [4] Eurachem — The Fitness for Purpose of Analytical Methods, third edition, 2025.
Consult the applicable full guidance for experimental designs and procedural requirements. These public overviews establish scope; this guide is not a substitute protocol or a claim of compliance. The worked scenario is fictional.
Continue learning
- Choose an analytical performance specification
- Understand method comparison
- Connect verification to IQC
- Interpret EQA evidence
Suggest a correction — please identify the page and passage concerned.