Detail of GB/Z 43280-2023

Introduction of GB/Z 43280-2023

GB/Z 43280-2023 Medical laboratories - Practical guidance for the estimation of measurement uncertainty 1 Scope This document provides practical guidance for the estimation and expression of the measurement uncertainty (MU) of quantitative measurand values produced by medical laboratories. Quantitative measurand values produced near the medical decision threshold by point-of-care testing systems are also included in this scope. This document also applies to the estimation of MU for results produced by qualitative (nominal) methods which include a measurement step. It is not recommended that estimates of MU be routinely reported with patient test results, but should be available on request. Note: See Annex B for an example of application of the MU. 2 Normative references There are no normative references in this document. 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: ——ISO Online browsing platform: available at https: //www .iso .org/obp ——IEC Electropedia: available at http: //www .electropedia .org/ 3.1 analyte component represented in the name of a measurand Example: In the measurand (measured quantity) "mass of total protein in 24-hour urine", "total protein" is the analyte (and “mass” is the property.) In "amount of substance concentration of glucose in plasma", "glucose" is the analyte (and “amount of substance concentration” is the property.) Note 1: Constituent of a sample with a measurable property. Note 2: JCGM 200:2012, 5.4, states that a primary measurement standard may be “…prepared by dissolving a known amount of substance of a chemical component to a known volume of solution”. [SOURCE: GB/T 29791.1-2013, 3.3, modified.] 3.2 calibration operation that, under specified conditions, in a first step, establishes a relation between the quantity values with associated measurement uncertainties provided by measurement standards (calibrators) and their corresponding indications and, in a second step, uses this relationship to establish a measurement result from an indication (for an unknown sample). Note 1: A calibration may be expressed by a statement, calibration function, calibration diagram, calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of the indication with associated MU. Note 2: Calibration should not be confused with adjustment of a measuring system, often mistakenly called “self-calibration”, nor with verification of calibration. Note 3: Often, the first step alone in the above definition is perceived as being calibration. [SOURCE: JCGM 200:2012, 2.39, modified] 3.3 calibrator measurement standard used in calibration Note 1: In this document, calibrator is synonymous with calibration material. Note 2: A calibrator is a measurement standard used in the calibration of a measuring system according to a specified measurement procedure. [SOURCE: JCGM 200:2012, 5.12] 3.4 commutability of a reference material property of a reference material, demonstrated by the closeness of agreement between the relation among the measurement results for a stated quantity in this material, obtained according to two measurement procedures, and the relation obtained among the measurement results for other specified materials Note 1: The reference material in question is usually a calibrator and the other specified materials are usually routine samples. Note 2: It is typical that there are more than two measurement procedures available and comparison among all applicable measurement procedures is desirable. Note 3: The requirement for the closeness of agreement shall be appropriate for the intended use of the reference material. Note 4: The commutability statement is restricted to the measurement procedures as specified in a particular comparison. [SOURCE: JCGM 200:2012, 5.15] 3.5 component constituent of a mixture the amount or concentration of which can be varied independently Note: See also analyte (3.1). [SOURCE: International Union of Pure and Applied Chemistry (IUPAC) Compendium of Chemical Terminology (Gold Book) Version 2.3.3 2014-02-24, modified.] 3.6 coverage factor k number larger than one by which a standard uncertainty value (u) is multiplied to obtain an expanded uncertainty, U (3.9) Notey: A coverage factor is usually symbolized k. [SOURCE: JCGM 200:2012, 2.38, modified.] 3.7 coverage interval interval containing the set of true quantity values of a measurand with a stated probability, based on the information available Note 1: A coverage interval does not need to be centred on the chosen measured quantity value (see JCGM 101:2008). Note 2: A coverage interval should not be termed “confidence interval” to avoid confusion with the statistical concept (see GUM: 1995, 6.2.2). Note 3: A coverage interval can be derived from an expanded MU (see GUM: 1995, 2.3.5). Note 4: The term ‘true’ is considered redundant by GUM. For this document the term ‘value of the measurand’ is used. [SOURCE: JCGM 200:2012, 2.36] 3.8 end-user calibrator end-user in vitro diagnostic medical device (IVD MD) calibrator reference material used as a measurement standard (calibrator) intended for use with one or more measurement procedures intended to examine a particular measurand in human samples 3.9 expanded measurement uncertainty expanded uncertainty U (multiplication) product of a u by a (coverage) factor k larger than the number one Note: A measured value x ± [k × u(y)], with coverage factor k= 2, means that the laboratory believes (≈95 % level of confidence) that the value of the measurand lies in the interval of values defined by the following formula: [SOURCE: JCGM 200:2012, 2.35, modified.] 3.10 external quality assessment; EQA international, national or local program designed to provide regular, external, independent quality assessment of a medical laboratory’s analytical performance, and assist in detecting bias of reported results compared to other laboratories. Note 1: Also known as Proficiency Testing (PT). Note 2: EQA is the term used in this document. 3.11 indication quantity value provided by a measuring instrument or a measuring system Note: An indication may be presented in visual or acoustic form or may be transferred to another device. An indication is often given by the position of a pointer on the display for analog outputs, a displayed or printed number for digital outputs, a code pattern for code outputs, or an assigned quantity value for material measures. [SOURCE: JCGM 200:2012, 4.1] 3.12 intermediate precision condition of measurement condition of measurement, out of a set of conditions that includes the same measurement procedure, same location, and replicate measurements on the same or similar objects over an extended period of time, but may include other conditions involving changes Note 1: The changes can include new calibrations, calibrators, operators, and measuring systems. Note 2: A specification for the conditions should contain the conditions changed and unchanged, to the extent possible. Note 3: For this document, the term long-term precision (uRw) is used to mean precision data for a given measurement procedure obtained over an extended period of time that at some point includes the effects of all or most changes in measuring conditions, for example, consumable lot changes, re-calibrations, etc. Such changes should be defined for each measurement procedure [see 3.33 repeatability condition of measurement; see 3.40 uncertainty component under conditions of within-laboratory precision (u Rw )]. Note 4: Changed conditions may include instrument maintenance where appropriate. Note 5: uRw is often the major contributor to the combined standard uncertainty of a measurement result in the medical laboratory. [SOURCE: JCGM 200:2012, 2.22] 3.13 internal quality control; IQC set of procedures and specified materials used by laboratory staff for the repetitive monitoring of analytical performance of measuring systems 3.14 long-term precision; uRw see 3.12, 3.40 Note: Both the term ‘long-term precision’ and the symbol u Rw are used in this document when refering to an uncertainty estimate based on data observed under intermediate precision conditions of measurement. 3.15 maximum allowable measurement uncertainty target measurement uncertainty maximum fit for purpose MU for measurement results produced by a given measurement procedure, and specified as an upper limit based on an evaluation of medical requirements Note 1: JCGM 200:2012, 4.26, defines maximum permissible measurement error. In modern English usage, the difference between the terms ‘allowed’ and ‘permitted’ is analogous to the difference between the concepts of tolerance (allowed) and authorization (permitted). Authorization implies a statutory, mandated, or legal requirement. For most measurands in laboratory medicine there are no legal limits of performance, therefore allowable is the preferred adjective in the context of this definition. Note 2: The maximum allowable MU is considered to represent fit-for-purpose performance based on use of a measurement result for a medical decision. [SOURCE: JCGM 200:2012, 2.34 and 4.26, modified.]

Contents of GB/Z 43280-2023