Important information to our customers concerning the quality of measurements

Importance of the topic

Analytical results underpin decisions across industry, regulatory, legal and medical contexts. Understanding and communicating the limitations of measurements — expressed as measurement uncertainty — is essential to avoid incorrect decisions such as unjustified rejection of products, wrongful legal outcomes, or unnecessary medical interventions. Clear reporting of uncertainty increases the reliability and comparability of test reports and supports fit-for-purpose use of analytical data.

Objectives and overview of the guidance

This document explains why laboratories are moving toward routine inclusion of measurement uncertainty in test reports and describes how such information should be interpreted by end users. It aims to improve decision making by providing a standardised approach to reporting and terminology so customers can better compare results from different providers and understand the confidence they can place in reported values.

Methodology and reporting practice

The guidance promotes reporting test results together with an uncertainty statement that defines an interval within which the true value is expected to lie at a specified confidence level (commonly 95%). Key elements:

• Measurement uncertainty is quantified as a combined standard uncertainty (uc) derived from identified error sources across the analytical process, including sampling, sample preparation, method performance and instrumentation.
• An expanded uncertainty (U) is reported by multiplying uc by a coverage factor k (typically k = 2), producing an interval approximating a 95% confidence level.
• Uncertainty can be presented in absolute terms (same units as the measurand) and/or relative terms (percentage of the measured value).

Illustrative example used in the guidance: total lead (Pb) reported as 1.65 mmol·kg-1 with an expanded uncertainty of ±0.15 mmol·kg-1 (9.1%), corresponding to an expected interval of 1.50–1.80 mmol·kg-1 at roughly 95% confidence.

Main results and discussion

The principal outcomes are conceptual rather than numerical: laboratories are encouraged to include uncertainty information more frequently in routine test reports, and to adopt consistent terminology aligned with international guides and standards. The document highlights several practical consequences:

• Decisions that compare analytical results to limit values require knowledge of uncertainty to avoid incorrect acceptance or rejection.
• Uncertainty reporting helps users judge whether a result is ‘‘fit for purpose’’ — neither over-specified (unnecessarily costly) nor under-specified (risking harm or non-compliance).
• Routine inclusion of uncertainty facilitates comparison between laboratories and supports regulatory and contractual transparency.
• When laboratories lack control over upstream steps (notably sampling and initial preparation performed by the customer), the uncertainty estimate may be incomplete; providing detailed sampling information reduces this source of error.

Benefits and practical use of the approach

Adoption of uncertainty-inclusive reporting yields concrete advantages:

• Improved decision quality: Users can weigh analytical results against limits with quantified confidence, reducing economic, legal and health risks.
• Better comparability: Shared terminology and reporting formats ease benchmarking across providers and time.
• Optimised resource use: Defining necessary accuracy avoids unnecessary analytical costs while ensuring sufficient information for decisions.
• Enhanced laboratory–client communication: Laboratories can advise customers on sampling and required accuracy levels, improving overall measurement quality.

Future trends and potential applications

Expected developments and opportunities include:

• Wider standardisation: Growing alignment with international guides will harmonise terminology and reporting practices across sectors and geographies.
• Digital reporting and metadata: Machine-readable uncertainty statements embedded in electronic reports will improve interoperability and automated decision workflows.
• Downstream integration: Regulators and industries may increasingly use uncertainty-aware thresholds and decision rules (e.g., guard-bands, probabilistic compliance assessment) rather than single-point comparisons.
• Improved sampling protocols: Recognition of sampling as a major uncertainty component will motivate better on-site procedures and clearer responsibilities between laboratories and clients.

Conclusion

Measurement uncertainty is a practical and necessary complement to reported analytical values. Routine inclusion of uncertainty statements—expressed clearly in absolute and/or relative terms and accompanied by the assumed confidence level—enables fit-for-purpose interpretation, reduces incorrect decisions, and enhances comparability of results. Effective implementation requires collaboration between laboratories and clients, particularly regarding sampling and pre-analytical steps.

Reference

SP Swedish National Testing and Research Institute. SP INFO 2000:27. Guidance on reporting measurement uncertainty in test reports. Based on SP INFO 2000:23 developed by SP and Föreningen Ackrediterade Laboratorier in collaboration with the National Food Administration, SWEDAC, the Swedish Environmental Protection Agency and the Swedish Water and Wastewater Association (VAV).