Pre- and post-analytical proficiency testing

Importance of the topic

Pre- and post-analytical activities (sample selection, sampling, preparation, interpretation, reporting and communication) contribute substantially to the overall quality of routine chemical and microbiological analyses. Errors or variability in these stages can negate otherwise accurate measurements and lead to incorrect decisions in clinical, regulatory and industrial settings. Proficiency testing (PT) and external quality assessment (EQA) schemes that include pre- and post-analytical components are therefore essential for assessing the full analytical pathway, improving harmonisation, and strengthening confidence in laboratory outputs.

Objectives and overview of the document

The original leaflet aims to illustrate the value and implementation possibilities of PT/EQA schemes that explicitly cover pre- and post-analytical steps. It provides practical examples to inspire scheme providers to develop assessments that probe the entire testing process rather than only the measurement phase. The document also situates these schemes within existing quality frameworks (e.g., ISO 15189) and highlights their role in harmonisation and guideline improvement.

Methodology

Pre- and post-analytical PT/EQA schemes are typically designed around realistic scenarios or simulated samples that require participants to perform decisions and actions representative of routine practice. Common methodological elements include:

• Scenario design: realistic case histories or samples that trigger choices about tests, sampling, or communication.
• Distribution of simulated or real, but homogenised, samples where appropriate.
• Requests for participants to submit procedural decisions, chosen methods, full results with uncertainties, interpretative comments and recommendations (e.g., pass/fail, notifications to authorities).
• Expert evaluation: panels or providers rank interpretative responses, judge conformity with standards, or supply model answers and commentary.
• Feedback reporting: comprehensive reports that compare participant actions, highlight good practice and deviations, and provide educational guidance.

Examples summarized

Four representative examples show how pre- and post-analytical PT/EQA can be structured and what they reveal:

• Interpreting clinical chemistry information: Participants receive patient background and analytical results and are assessed on interpretative advice and clinical recommendations. Scoring and narrative feedback reveal variation in clinical interpretation.
• Sampling requests in microbiology: A food-poisoning scenario asks participants which organisms/toxins to test and how they would communicate findings. The scheme evaluates sampling strategy, test selection and public-health reporting decisions.
• Toy testing: Providers distribute toy samples and require participants to identify applicable clauses of a standard (EN 71), select relevant tests and state labeling requirements. The exercise exposes differences in standard application and test selection.
• Monitoring drinking water quality: A synthetic drinking-water sample near regulatory limits is used to test whether participants report results, estimate uncertainties and make correct pass/fail recommendations in line with Directive 98/83/EC, supporting regulatory dialogue and education.

Main results and discussion

Across the examples, pre- and post-analytical PT/EQA schemes consistently reveal issues that purely analytical PT would miss: inconsistent adherence to guidelines, variable sample-preparation choices, divergent interpretative decisions and gaps in communication to stakeholders. Key discussion points include:

• Harmonisation potential: Scheme results identify common deviations and knowledge gaps, providing evidence to update guidance and harmonise practices across laboratories.
• Educational value: Detailed feedback and model answers support targeted training and continuous improvement.
• Regulatory relevance: Post-analytical assessments (e.g., pass/fail recommendations for drinking water) can inform regulators and support public-health protection.
• Design challenges: Creating realistic scenarios that adequately mimic routine workflows, ensuring participant engagement, and objectively scoring interpretative responses require careful planning and expert input.

Benefits and practical applications

Pre- and post-analytical PT/EQA schemes offer several practical benefits:

• Comprehensive quality assessment covering the entire testing process rather than only measurement accuracy.
• Identification of non-analytical error sources (sampling, interpretation, reporting) that threaten result utility.
• Support for accreditation requirements (for example, ISO 15189 emphasis on entire process assessment).
• Evidence base for revising national or international standards and laboratory guidelines.
• Improved communication pathways between laboratories, clinicians, public-health bodies and regulators.

Future trends and potential uses

Emerging directions and opportunities to enhance pre- and post-analytical PT/EQA include:

• Digital and virtual case simulations to complement physical sample distribution, allowing scalable testing of interpretative and reporting skills.
• Integration of laboratory information systems (LIS) and electronic reporting into schemes to evaluate end-to-end digital workflows.
• Advanced analytics and benchmarking tools to cluster participant behaviours, detect systemic issues, and personalise feedback.
• Cross-sector PT schemes that bridge clinical, environmental and food-testing communities for harmonised practice.
• Closer alignment with accreditation and regulatory frameworks so scheme outputs can directly inform compliance and policy decisions.

Conclusion

Incorporating pre- and post-analytical elements into PT/EQA broadens the scope and value of external quality assessment. Such schemes reveal process weaknesses that analytical-only assessments overlook, facilitate harmonisation, support accreditation, and provide actionable feedback to laboratories, clinicians and regulators. Carefully designed scenarios, expert evaluation and educational reporting are central to their success.

References

• Eurachem Proficiency Testing Working Group. Pre- and post-analytical proficiency testing. Second English edition, July 2022. Produced by Eurachem.