Overview
ISO/TS 20914:2019 - "Medical laboratories - Practical guidance for the estimation of measurement uncertainty" provides a pragmatic, laboratory-focused approach to estimating and expressing measurement uncertainty (MU) for quantitative and certain qualitative results produced in medical laboratories. The Technical Specification supports compliance with ISO 15189 requirements by describing a top‑down, GUM‑informed methodology that uses laboratory internal quality control (IQC) data and available manufacturer information to produce usable MU estimates. Point‑of‑care testing (POCT) results near medical decision thresholds and qualitative methods that include a measurement step are explicitly within scope. The specification notes that MU estimates need not be routinely appended to patient reports but should be made available on request.
Key topics and requirements
- Measurement uncertainty concept - practical definition and purpose for medical decision‑making.
- Maximum allowable measurement uncertainty - considerations when comparing MU to clinical requirements.
- Sources of uncertainty - internal precision (IQC), calibrator uncertainty, bias, reagent/lot effects, counting uncertainty and other contributors.
- Expression of MU - using standard and expanded uncertainty, coverage factors and coverage intervals consistent with metrological practice.
- Use of relative standard uncertainty - guidance on calculations where appropriate.
- Reporting and availability - MU should be available on request; routine reporting with patient results is not recommended.
- Stepwise estimation process - measurand definition, assessment of precision, handling reagent or lot changes, multiple measuring systems, uncertainty of end‑user calibrators, bias assessment, re‑estimation intervals, and limitations.
- Annexes with worked examples - illustrative examples and an application of MU to result interpretation (Annex A and B).
Practical applications and users
ISO/TS 20914:2019 is intended for:
- Clinical laboratory directors and technical staff implementing ISO 15189 compliance.
- Quality managers developing MU estimation procedures and documentation.
- Medical laboratory scientists and POCT coordinators interpreting results near clinical decision limits.
- Manufacturers and calibrator suppliers providing uncertainty data for end‑user use.
Practical uses include demonstrating suitability of analytical performance against clinical requirements, informing result interpretation close to decision thresholds, identifying steps to reduce MU, and supporting communication with clinicians when MU is requested.
Related standards
- ISO 15189 - Medical laboratories - Requirements for quality and competence (links MU requirement).
- JCGM 100/ GUM - Guide to the expression of uncertainty in measurement (foundational metrology guidance referenced by this TS).
Keywords: ISO/TS 20914:2019, measurement uncertainty, medical laboratories, MU, ISO 15189, point‑of‑care testing, internal quality control, calibrator uncertainty, GUM.