measurement uncertainty

Measurement uncertainty describes the dispersion of values that could reasonably be attributed to the quantity being measured, using the information available. It is not a known mistake, a tolerance limit, or a correction applied to a result. For quantitative laboratory examinations, an estimate often draws on long-term imprecision and relevant information about calibration or bias, with care to avoid counting the same contribution twice.

An uncertainty statement should identify the measurand, concentration or range, estimation approach, relevant components, and any coverage factor used for expanded uncertainty. Its usefulness depends on the clinical question and the quality of the underlying data. Review estimates after important changes, and distinguish analytical uncertainty from biological variation and pre-examination influences that may require separate consideration.

Accreditation assessment examines whether uncertainty is evaluated where relevant and whether staff understand its implications for intended use. A spreadsheet alone is insufficient without an explanation of data selection and assumptions. Consider uncertainty when results approach decision thresholds, while recognizing that clinical interpretation also depends on patient context and other sources of variation.