MEASUREMENT UNCERTAINTY
effectiveness, as endorsed by ISO/TS 20914:2019. This approach is particularly suitable for medical laboratories, as it considers the specific use of the measurand in medical decision-making and patient management, which is essential for diagnostic, prognostic, monitoring, and therapy purposes. The ‘bottom-up’ approach, while detailed, is often seen as overly complex and not adding significant value in the context of medical laboratories. Having a clear understanding between laboratory and clinical staff is essential for reporting MU, and this includes the method chosen for MU calculation.
n Criteria for reporting measurement uncertainty Some criteria are mandated, and some are just good practice. The requirements may differ so processes should be aligned with potential requests for MU estimates.
1. Clinical Trial Monitoring
Reviewing and reporting measurement uncertainty is integral to maintaining the accuracy and reliability of medical laboratory tests.
n Using MU to retest patients after a control failure
If results have been provided in a time where the IQC was out of control, one approach is to use MU directly when retesting patients once the measurement procedure is back under stable control. Retesting a sample of patients and determining whether there is a difference, including MU, that is clinically unacceptable indicates the need for an amended report. The samples tested can be a small sample of results, randomly chosen, or specifically chosen at clinical decision points where patient outcomes may be most impacted. The decision on which method to use should be related to the clinical utility of the assay. Ideally, all patient samples would be retested. However, resource and time limitations may not make this possible. This highlights the importance of running QC at intervals that allow the laboratory time to identify and correct an issue before clinical interventions occur.
Roles of stakeholders in ensuring compliance with MU limits Throughout this series, the importance of various stakeholders in assay performance has become clear. Laboratories are reliant on the stated performance of reference materials from reference laboratories and IVD manufacturers to ensure consistent attainment of performance specifications. Degradation in the performance of materials used for metrological
traceability and calibration can introduce uncertainty into the measurement system that the local laboratory cannot control. Laboratories must be aware of the impact of such uncertainty ‘drift’ so that troubleshooting does not focus solely on local laboratory imprecision. This is achievable as long as laboratories are provided with all required metrological traceability information, including the uncertainty of the calibration to the higher reference standard or procedure.
Reporting measurement uncertainty
n To whom should measurement uncertainty be reported?
Firstly, current recommendations remain that uncertainty is provided upon request, and is not needed to be routinely provided on clinical reports. However, when it is requested, by clinicians or other parties, there are things to consider. Understanding and applying the
appropriate methodologies for estimating MU is crucial. The ‘top-down’ approach is recommended for its simplicity and
Requirements n Good Clinical Practice (GCP) Guidelines: Follow GCP guidelines to ensure accurate and reliable MU data reporting during clinical trials. This adherence is essential for the validity of trial outcomes.
n Data Integrity: Ensure that MU data are accurately documented and reported to support the integrity of the trial data.
2. Accreditation Requirements Against
National and International Standards n ISO 15189 Compliance: Laboratories must ensure that MU reporting meets the standards set by ISO 15189. This involves clear and accurate documentation of MU for regulatory compliance and quality assurance.
n Other Standards: Compliance with standards from organisations like CLIA and CAP is also required depending on your laboratory’s location. These standards specify criteria for MU reporting, ensuring consistency and reliability.
3. Considerations for Laboratory Staff n Understanding MU Implications: Staff
must grasp the implications of MU on test results and patient outcomes.
Quality managers and leads oversee the review of MU, with the ultimate goal of ensuring that all procedures align with accreditation standards and quality protocols
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