Technical Specification
Track updates
SA TS ISO 20914:2021
[Current]Medical laboratories — Practical guidance for the estimation of measurement uncertainty
Identically adopts ISO/TS 20914:2019, which 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 included. Applies to the estimation of MU for results produced by qualitative (nominal) methods which include a measurement step. KEYWORDS: medical laboratories measurement uncertainty guidance
Published: 12/02/2021
Pages: 73
Table of contents
Cited references
Content history
Table of contents
Header
About this publication
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Abbreviated terms and symbols
5 Measurement uncertainty for medical laboratories
5.1 Measurement uncertainty concept
5.2 Maximum allowable measurement uncertainty
5.3 Sources of measurement uncertainty
5.4 Expression of measurement uncertainty
5.5 Use of relative standard uncertainty for calculating uncertainty estimates
5.6 Reporting measurement uncertainty
6 Steps for estimating uncertainty of measurand values
6.1 Measurand definition
6.2 Measurement precision
6.3 Effect of reagent and internal quality control lot changes on estimating uncertainty
6.4 Laboratories using multiple measuring systems for the same measurand
6.5 Uncertainty of end-user calibrator values (ucal)
6.6 Measurement bias
6.7 Process overview for estimation of measurement uncertainty
6.8 Re-estimation of measurement uncertainty
6.9 Qualitative results based on numerical results
6.10 Uncertainty of counting entities
6.11 Limitations of measurement uncertainty estimates
Annex A
A.1 Introduction
A.2 Basic calculations
A.2.1 Standard deviation and variance (see3.36, 3.40)
A.2.2 Example — Calculation of uRw under long-term precision conditions
A.2.3 Example — Calculation of ur(y) under repeatability conditions
A.2.4 Combining independent standard measurement uncertainties
A.3 Measurement uncertainty across changes to measuring conditions
A.3.1 General approach to calculation
A.3.2 Estimation of u(y) using multiple lots of reagent, where internal quality control shifts are observed without a corresponding shift in patient values
A.3.3 General approach for estimation of uRw using multiple lots of internal quality control
A.4 Pooled average standard uncertainty among several identical measuring systems, accounting for different internal quality control mean values
A.5 Uncertainty of anion gap (AG) results using internal quality control data
A.6 Uncertainty of results for estimated glomerular filtration rate (eGFR)
A.6.1 Estimation of uncertainty of estimated glomerular filtration rate, u(eGFR)
A.6.2 Examples of estimated glomerular filtration formulas in a format suitable for processing with a typical commercial spreadsheet
A.7 Estimation of expanded uncertainty for number concentration of white blood cells in whole blood
A.8 Estimation of uncertainty of amount of substance concentration of albumin in serum/plasma – comparing uncertainty estimates using relative uncertainties vs. standard uncertainties
A.8.1 Uncertainty of amount of substance concentration of albumin in serum/plasma calculated with standard uncertainties
A.8.2 Uncertainty of amount of substance concentration of albumin in serum/plasma calculated using relative standard uncertainties, urel
A.9 Calculating % Urel for international Normalised Ratio
A.10 Uncertainty for a human immunodeficiency virus type 1 viral load measurement
A.11 Uncertainty of BCR-ABL1 measurement using one lot of internal quality control material
A.12 Uncertainty of rubella IgG antibody measurement
A.13 Uncertainty of hepatitis B surface antigen measurement
A.14 Uncertainty of number concentration of red blood cells and total WBC in urine using a manual method
Annex B
Annex C
C.1 GUM and measurement uncertainty for medical laboratories
C.2 Practical approach to measurement uncertainty in medical laboratories
C.3 Quantity value of a measurand
C.4 Uncertainty of values assigned to end-user calibrators (ucal)
C.5 Estimation of the uncertainty of a bias correction (ubias)
C.5.1 Overview of key concepts and process
C.5.2 Deciding if the estimated measurement bias is significant
C.5.3 Incomplete data for estimation of ubias
C.5.4 Uncertainty of measured values corrected for measurement bias, u(ycorr)
C.6 Worked examples of bias correction (ubias)
C.6.1 Example 1 — Estimation of ubias when correcting a bias using a commutable certified reference material (CRM)
C.6.2 Example 2 — Estimation of uncertainty incorporating bias correction and long-term precision across two lot numbers of IQC material
C.7 Example of direct calculation of estimated relative uncertainty
Bibliography
Cited references in this standard