Measurement uncertainty for clinical laboratoriesa revision of the. Where we have numeric data measurement uncertainty can be expressed as the standard deviation or as the coefficient of. Pdf uncertainty of measurement in medical laboratories. Assessing the measurement uncertainty of qualitative. N2 the result of a measurement is only an estimate of the value of the measurand and it is complete only when accompanied by a statement of the measurement uncertainty. The old clinical pathology accreditation cpa standard advocated that we determine the uncertainty of results where possible. In todays global world, accurate, reliable and comparable measurement results are of vital importance. In clinical chemistry and laboratory medicine, mu assessment is required as a. In measurement procedures that are reported in qualitative terms based on a quantitative measurement, the uncertainty at the thresholds for a qualitative interpretation should be considered when making the qualitative assessment. The iso 15189 standard requires that the laboratory shall determine measurement uncertainty for each measurement procedure. Because measurement uncertainty is concerned with analytical and not physiological variability, it includes the consideration of bias but does not consider or incorporate biological variation.
Uncertainty of measurement in laboratory medicine ncbi. Although not commonly reported with results, the calculation of measurement uncertainty mu has become common in routine clinical laboratories. As soon as we move into the laboratory and start quantifying various properties of our samples, we also move into metrology, which is the science of measurement and its applications. Apr 24, 2020 understanding and calculating uncertainty in the clinical laboratory.
Mar 20, 2012 calculation of uncertainty of measurement in clinical laboratory using intra laboratory qc and external proficiency testing data. Pdf uncertainty of measurement in laboratory medicine. Uncertainty in measurement introduction and examples. Th e res ult of a me asurement is onl y an estimat e of the value of the m easur and and it i s comp lete o nly wh en acc ompanie d by. This guideline explains the concept, estimation, and application of measurement uncertainty in the field of clinical laboratory medicine. Uncertainty is always present and comes in different forms. Clsi ep29 expression of measurement uncertainty in. International union of pure and applied chemistry, international federation of clinical chemistry. Measurement uncertainty for medical laboratories status.
The laboratory shall determine measurement uncertainty for each 5. Frequently, this is simplified to only dispersion, and measurement uncertainty is obtained using statistical. Measurement uncertainty is a parameter used in data processing for the description of both the dispersion of the result and its estimated difference from the accurate value. Assessing the measurement uncertainty of qualitative analysis. Aug 01, 2016 the uncertainty of a measurement result is a fundamental concept in metrology indicating the range within the true value of a measurement should lie.
Time to engage in measurement uncertainty westgard. Uncertainty in measurement introduction and examples from. Measurement verification in the clinical laboratory. Measurement uncertainty for clinical laboratories a revision of the concept. Issues and challenges in applicability of measurement uncertainty estimation in medical laboratories. Random and systematic errors can act together to produce an error of measurement total error and generate a doubt uncertainty about the. Let us examine this example that is a simplification of an article in clinical chemistry and laboratory medicine. An assessment of the laboratory and clinical implications of. Measurement uncertainty how to calculate it in the. But what does it mean to have measurement uncertainty in the laboratory. Hitchhikers guide to measurement uncertainty mu in clinical. The recommendations provided are consistent with the guide to the expression of uncertainty in measurement gum 1 and with the international organization for standardization iso standards concerned with. Uncertainty, or rather measurement uncertainty mu, is such a term. Measurement uncertainty in laboratory medicine was published in january 2012 the code changed to ep29a without text revision and it is the only global guideline for the determination of.
Measurement uncertainty how to calculate it in the medical laboratory godfrey c. Pdf measurement uncertainty calculation in clinical. Eurachem 2000 quantifying uncertainty in analytical measurement. Measurement uncertainty calculation in clinical laboratories. It provides labs with an indication of potential sources of uncertainty. In the ongoing war of words in the lab, its time to hear another voice. The clinical and laboratory standards institute clsiifcc c51a expression of measurement uncertainty in laboratory medicine was published in january 2012 the code changed to ep29a without text revision and it is the only global guideline for the determination of measurement uncertainty. Whether you are measuring an object with a ruler, weighing items on a scale, or running complex assays, you will never be able to achieve exactly the same measurement every time. Uncertainty is an unavoidable part of any measurement and it begins to matter when results are close to a specified limit. It provides quantitative evidence that measurement results adhere to the clinical requirements for reliability. Uncertainty of measurement in medical laboratories. An extensive evaluation and surveillance of clinical laboratory performance is a part of laboratory accreditation. Dietmar stockl, an expert from across the atlantic, provides us with a detailed essay explaining how measurement uncertainty can be useful to the. A guide on measurement uncertainty in medical testing.
A statement of uncertainty of the result of a laboratory test provides this information. National pathology accreditation advisory council, australian government department of health and ageing, 2007. However, when used in a technical sense it carries a specific meaning. International standards requiring traceability of lab. Greg cooper, cls, cqa, mha, is a californialicensed clinical laboratory scientist, holds a masters degree in healthcare administration, and recently retired after more than 30 years of service in the.
Approved guideline this guideline describes a practical approach to assist clinical laboratories in developing and calculating useful estimates of measurement uncertainty, and illustrates their application in maintaining and improving the quality of measured values used in patient care. Comparison of manufacturers performance claims with data collected in the laboratory. Labs need to carry out mu as it is a requ irement of iso 15189. Measurement uncertainty is specifically mentioned in section 5. Calculation is performed using program written in visual basic for. It is a parameter, associated with the result of a measurement e. The term uncertainty of measurement is preferred to measurement uncertainty, the former being the term of choice in isoiec 17025 and iso 15189, and of organisations such as the international federation of clinical chemistry ifcc and the national committee for clinical laboratory standards nccls.
It relates to the doubt that exists for the result of any measurement. Kristiansen description of a generally applicable model for the evaluation of uncertainty of measurement in clinical chemistry. Institutional guidelines for estimating uncertainty of measurement, containing examples in fields of application other than clinical laboratory sciences, have been published. Measurement uncertainty an overview sciencedirect topics. It also states that upon request, the laboratory shall make its estimates of measurement uncertainty available to laboratory users. Uncertainty in measurement introduction and examples from laboratory medicine author anders kallner, dept. The laboratory shall define the performance requirements for the measurement uncertainty. Calculation of uncertainty of measurement in clinical laboratory using intralaboratory qc and external proficiency testing data. An adequate assessment of the measurement uncertainty in a laboratory medicine is one of the most important factors for a reliable interpretation of the results. The laboratory shall determine measurement uncertainty for each.
Results with larger measurement uncertainty intervals have a significant probability of being unrealistic, arising a high risk of the uncorrected clinical decision. Sep 01, 2000 institutional guidelines for estimating uncertainty of measurement, containing examples in fields of application other than clinical laboratory sciences, have been published. Padoan a antonelli g aita a sciacovelli l plebani m. A proper evaluation of uncertainty is good professional practice and can provide laboratories and customers with valuable information about the quality and reliability of the result. An adequate assessment of the measurement uncertainty in a laboratory. Estimation of uncertainty measurement a prerequisite of. The international vocabulary of metrology defines uncertainty as a parameter that expresses the dispersion of the values of a measurement. Uncertainty of measurement in laboratory medicine in. The concept of uncertainty can also be used for other purposes than measurements and it can include for instance preanalytical and post analytical sources of uncertainty. Measurement uncertainty how to calculate it in the medical. Assessment of the measurement uncertainty is recommended in qualitative analyses in clinical laboratories.
Therefore, clinical laboratories should report measurement results, which are expressed by a coverage interval that includes the measurement value and its measurement uncertainty 12. The use of measurement uncertainty on clinical laboratories. Let us examine this example that is a simplification of an article in clinical chemistry and laboratory medicine 6. Define and discuss measurement uncertainty, as it relates to test performance. Measurement uncertainty for clinical laboratories a. Measurement uncertainty budget uncertainty of references measurand definition patient result uncertainty reference provider ivd manufacturer clinical laboratory although independent in the tasks, their performances contribute together to the total mu budget. An assessment of the laboratory and clinical implications of estimated bias upon.
This guideline describes a practical approach to assist clinical laboratories in developing and calculating useful estimates of measurement uncertainty, and illustrates their application in maintaining and improving the quality of measured values used in patient care. Compendium of terminology and nomenclature of properties in clinical laboratory sciences recommendations 1995. Measurement uncertainty mu estimation has been introduced by iso 15189 for the accreditation of clinical laboratories. In ordinary use, the word uncertainty does not inspire confidence.
Method validation and measurement uncertainty biochemia. The laboratory shall determine measurement uncertainty for each measurement procedure in the examination phase used to report measured quantity values on patients samples. A flow chart to the selection of models for the determination of measurement uncertainty in a medical laboratory is recommended. Klee, yuehwern yih laboratory medicine and pathology. This guideline is intended for clinical laboratories and in vitro diagnostic ivd device manufacturers. Expression of measurement uncertainty in laboratory medicine approved guideline, clinical and laboratory standards institute clsi. Treatment of bias in estimating measurement uncertainty. Standards such as iso 15189 require that laboratories must determine uncertainty for each test. Therefore, the standards which regulate laboratory requirements isoiec 17025, iso 15189 demand a metrological approach to the measurement processes, requiring method validation, establishment of metrological traceability, estimation of measurement uncertainty, monitoring of trends in.
The measurement uncertainty is estimated as 2 s where s is a standard deviation which estimates the imprecision. Experimental confirmation of the key analytical components of measurement uncertainty, i. There are human and other preanalytical sources of variation the manner in which a specimen is collected, handled, or shipped and the storage conditions to which it was exposed, and these can lead to either random or systematic variation. The guidance treats measurement uncertainty as the imprecision i. Measurement uncertainty of measured quantity values iso15189 requires that the laboratory shall determine the measurement uncertainty for procedures used to report measured quantity values on patients samples. Uncertainty associated with microbiological analysis. Measurement uncertainty mu relates to the margin of doubt that exists for the result of any measurement, as well as how significant the doubt.
Hitchhikers guide to measurement uncertainty mu in. Uncertainty of measurement and clinical value of semen. Master guidance on measurement uncertainty for medical. The laboratory shall determine measurement uncertainty for each measurement procedure in the examination phases used to report measured quantity values on patients samples. Uncertainty of measurement in clinical laboratory sciences.
It is defined as an attempt to identify all events in a measurement procedure that could cause a dispersion of the results, quantify the dispersion, and summarize it in one expression known as the combined uncertainty. Uncertainty of measurement in medical laboratories intechopen. Clinical laboratory testing is a vital component of many stages of the medical decision making process, and therefore information about the quality of the measurement process is critical to the medical decisionmaking process. Measurement uncertainty is defined as the nonnegative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on. Kristiansen counterpoint the guide to expression of uncertainty in measurement approach for estimating uncertainty. Definitions of measurement uncertainty here are four definitions of measurement uncertainty. Measurement uncertainty is the margin of uncertainty, or doubt, that exists about the result of any measurement there is always margin of doubt associated with any measurement as well as the confidence in that doubt, which states how sure we are that the true value is within that margin. The use of measurement uncertainty on clinical laboratories results. The uncertainty arises from different causes of variation involved in measurement. Measurement uncertainty is a parameter that is associated with the dispersion of measurements.
Petr klapetek, in quantitative data processing in scanning probe microscopy, 20. Importance of measurement uncertainty estimate in medical. Evaluating measurement uncertainty in clinical chemistry. The measurement uncertainty mu is a parameter, associated with the result of a. Uncertainty of measurement in quantitative medical testing. Expression of measurement uncertainty in laboratory.
Ontario laboratory accreditation ola first outlined its ex pectations with regard to traceability and measurement. Using sigma metrics and measurement uncertainty in qc. What types of laboratory measurement should use mu. Although mu reporting is not required, its inclusion in medical reports is of potential assistance to physicians in results interpretation.
The accuracy, precision, and fitnessforpurpose of medical laboratory results rely on the basic metrological concepts of a common system of units, traceability of measured values, uncertainty of measurement measurement uncertainty or mu, and commutability of results within a calibration hierarchy. Expression of measurement uncertainty in laboratory medicine. Uncertainty of measurement in clinical microbiology. To clarify the laboratorys responsibility and the caps 15189 assessment standards, we have developed this interpretive document for the purposes of accreditation. The laboratory shall determine measurement uncertainty for each measurement procedure, in the examination ph ases used to report measured quantity values on patients samples. We seek to know the true value of an analyte measurand in a patient sample.
752 1066 77 949 437 527 1481 180 1492 1353 1568 906 1229 271 835 819 1315 800 865 1584 1567 1035 1166 398 1010 926 1070 1466 758 673 1470 576