The top-down approach to measurement uncertainty

Introduction: By quantifying the measurement uncertainty (MU), both the laboratory and the physician can have an objective estimate of the results’ quality. There is significant flexibility on how to determine the MU in laboratory medicine and different approaches have been proposed by Nordtest, Eurolab and Cofrac to obtain the data and apply them in formulas. The purpose of this study is to compare three different top-down approaches for the estimation of the MU and to suggest which of these approaches could be the most suitable choice for routine use in clinical laboratories. Materials and methods: Imprecision and bias of the methods were considered as components of the MU. The bias was obtained from certified reference calibrators (CRC), proficiency tests (PT), and inter-laboratory internal quality control scheme (IQCS) programs. The bias uncertainty, the combined and the expanded uncertainty were estimated using the Nordtest, Eurolab and Cofrac approaches. Results: Using different approaches, the expanded uncertainty estimates ranged from 18.9-40.4%, 18.2-22.8%, 9.3-20.9%, and 7.1-18.6% for cancer antigen (CA) 19-9, testosterone, alkaline phosphatase (ALP), and creatinine, respectively. Permissible values for MU and total error ranged from 16.0-46.1%, 13.1-21.6%, 10.7-26.2%, and 7.5-17.3%, respectively. Conclusion: The bias was highest using PT, followed by CRC and IQCS data, which were similar. The Cofrac approach showed the highest uncertainties, followed by Eurolab and Nordtest. However, the Eurolab approach requires additional measurements to obtain uncertainty data. In summary, the Nordtest approach using IQCS data was therefore found to be the most practical formula.

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REASSESSMENT OF UNCERTAINTY EXPANSION BY LINEAR ADDITION OF LONG-TERM COMPONENTS FROM TOP-DOWN INFORMATION

Radiocarbon ◽

10.1017/rdc.2021.96 ◽

2021 ◽

pp. 1-15

Author(s):

G Salazar ◽

S Szidat

Keyword(s):

Mass Spectrometry ◽

Measurement Uncertainty ◽

High Precision ◽

Accelerator Mass Spectrometry ◽

Expanded Uncertainty ◽

Top Down ◽

Bottom Up ◽

Linear Addition

ABSTRACT Since radiocarbon accelerator mass spectrometry (14C AMS) is considered a high-precision technique, reassessment of the measurement uncertainty has been a topic of interest. Scientists from analytical and metrological fields have developed the top-down and bottom-up measurement of uncertainty approaches. The 14C quoted error should approximate the uncertainty of long-term repetitions of the top-down approach in order to be realistic. The novelty of this paper is that the uncertainty of both approaches were approximated to each other. Furthermore, we apportioned the graphitization, instrumentation, and bias components in order to additively expand the quoted error. Our results are comparable to error multipliers and to long-term repeatability studies reported by other laboratories. Our laboratory was established in late 2012 with N2 as stripper gas and 7 years later, we changed to helium stripper. Thus, we were able to compare both gases, and demonstrate that helium is a better stripper gas. In absolute F14C units, the ranges of graphitization+bias combined uncertainties were (0.7 to 4.1) × 10–3 for N2 and (0.7–3.0) × 10–3 for He depending on the standard 14C content. The error multiplier for He defined as the expanded uncertainty over quoted error, in average, was 1.7; while without the bias, the multiplier was 1.3.

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Comparison between bottom-up and top-down approaches in the estimation of measurement uncertainty

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2014-0801 ◽

2015 ◽

Vol 53 (7) ◽

Cited By ~ 12

Author(s):

Jun Hyung Lee ◽

Jee-Hye Choi ◽

Jae Saeng Youn ◽

Young Joo Cha ◽

Woonheung Song ◽

...

Keyword(s):

Measurement Uncertainty ◽

Uncertainty Budget ◽

Internal Quality ◽

Systematic Bias ◽

Top Down ◽

Bottom Up ◽

Sources Of Uncertainty ◽

Clinical Laboratories ◽

Measurement Results ◽

Low Glucose

AbstractMeasurement uncertainty is a metrological concept to quantify the variability of measurement results. There are two approaches to estimate measurement uncertainty. In this study, we sought to provide practical and detailed examples of the two approaches and compare the bottom-up and top-down approaches to estimating measurement uncertainty.We estimated measurement uncertainty of the concentration of glucose according to CLSI EP29-A guideline. Two different approaches were used. First, we performed a bottom-up approach. We identified the sources of uncertainty and made an uncertainty budget and assessed the measurement functions. We determined the uncertainties of each element and combined them. Second, we performed a top-down approach using internal quality control (IQC) data for 6 months. Then, we estimated and corrected systematic bias using certified reference material of glucose (NIST SRM 965b).The expanded uncertainties at the low glucose concentration (5.57 mmol/L) by the bottom-up approach and top-down approaches were ±0.18 mmol/L and ±0.17 mmol/L, respectively (allWe presented practical and detailed examples for estimating measurement uncertainty by the two approaches. The uncertainties by the bottom-up approach were quite similar to those by the top-down approach. Thus, we demonstrated that the two approaches were approximately equivalent and interchangeable and concluded that clinical laboratories could determine measurement uncertainty by the simpler top-down approach.

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Reliability of measurement uncertainty estimates for forensic analyses: evidence from recent proficiency tests

Accreditation and Quality Assurance ◽

10.1007/s00769-016-1211-2 ◽

2016 ◽

Vol 21 (3) ◽

pp. 211-219 ◽

Cited By ~ 1

Author(s):

Jack Wallace

Keyword(s):

Measurement Uncertainty ◽

Proficiency Tests ◽

Uncertainty Estimates

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An automated terminal quality control scheme

Aircraft Engineering and Aerospace Technology ◽

10.1108/eb034983 ◽

1973 ◽

Vol 45 (1) ◽

pp. 21-24

Keyword(s):

Quality Control ◽

Control Scheme ◽

Quality Control Scheme

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Estimation of uncertainty in olfactometry

Water Science & Technology ◽

10.2166/wst.2009.108 ◽

2009 ◽

Vol 59 (7) ◽

pp. 1409-1413 ◽

Cited By ~ 5

Author(s):

T. Higuchi

Keyword(s):

Measurement Uncertainty ◽

Interlaboratory Comparison ◽

Collaborative Study ◽

Estimation Procedure ◽

Measurement Model ◽

Standard Uncertainty ◽

Expanded Uncertainty ◽

Collaborative Test ◽

Measurement Results ◽

Estimation Of Uncertainty

Estimation of uncertainty in odour measurement is essential to the interpretation of the measurement results. The fundamental procedure for the estimation of measurement uncertainty comprises the specification of the measurement process, expression of the measurement model and all influences, evaluation of the standard uncertainty of each component, calculation of the combined standard uncertainty, determination of a coverage factor, calculation of the expanded uncertainty and reporting. Collaborative study such as interlaboratory comparison of olfactometry yields performance indicators of the measurement method including repeatability and reproducibility. Therefore, the use of collaborative test results for measurement uncertainty estimation according to ISO/TS 21748 and ISO 20988 is effective and reasonable. Measurement uncertainty of the triangular odour bag method was estimated using interlaboratory comparison data from 2003 to 2007 on the basis of the simplest model of statistical analysis, and the expanded uncertainty of odour index ranged between 3.1 and 6.7. On the basis of the establishment of the estimation procedure for uncertainty, a coherent interpretation method for the measurement results will be proposed and more effective and practical quality control of olfactometry will be available.

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Paracetamol: A Report of a Regional Quality Control Scheme

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456327901600167 ◽

1979 ◽

Vol 16 (1-6) ◽

pp. 265-270 ◽

Cited By ~ 2

Author(s):

J. Epton

Keyword(s):

Quality Control ◽

Group Performance ◽

Clinical Importance ◽

External Quality Control ◽

External Quality ◽

Limits Of Detection ◽

Trouble Shooting ◽

Control Scheme ◽

Considerable Impact ◽

Quality Control Scheme

The results from an external quality control scheme for the assay of paracetamol in serum are reported. A preferential method of assay has not become evident, but, as a result of the scheme, some laboratories have changed or modified their techniques or have re-established the limits of detection. The majority of laboratories were able to estimate paracetamol satisfactorily at those levels which are of clinical importance. The overall group performance has shown little change. The programme has had considerable impact in so far as it has led to a mutually useful interchange of information and trouble shooting.

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Data warehouse quality control scheme for electricity market analysis

Computational Intelligence in Industrial Application ◽

10.1201/b18590-77 ◽

2015 ◽

pp. 393-398

Author(s):

YanMin Guo ◽

SuYan Long ◽

GaoQin Wang ◽

ZhongYuan Chen ◽

HaiChao Wang ◽

...

Keyword(s):

Quality Control ◽

Data Warehouse ◽

Electricity Market ◽

Market Analysis ◽

Control Scheme ◽

Data Warehouse Quality ◽

Quality Control Scheme

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The Italian Quality Control Scheme for Crossmatching Procedures and HLA Sera Screening: The 2002 Pilot Study

Archives of Pathology & Laboratory Medicine ◽

10.5858/2005-129-1470-tiqcsf ◽

2005 ◽

Vol 129 (11) ◽

pp. 1470-1475

Author(s):

Raffaele Conca ◽

Loredana Praticò-Barbato ◽

Anna Maria Dall'Omo ◽

Antonio Amoroso

Keyword(s):

Quality Control ◽

Serum Antibody ◽

Hla Typing ◽

European Federation ◽

Antibody Specificity ◽

Control Scheme ◽

National Quality ◽

Transplant Immunology ◽

Quality Control Scheme

Abstract Context.—The first national quality control (QC) program of histocompatibility serum testing was performed in Italy in 2002. Objective.—To monitor the performance of HLA typing laboratories while meeting the accreditation requirements of the European Federation for Immunogenetics (EFI), which require HLA typing laboratories to participate in external QC of their crossmatch and antibody analyses. Design.—The Turin Transplant Immunology Service was asked to organize a QC survey of 17 HLA typing laboratories in Italy. Each laboratory received 12 serum specimens and 6 blood samples and was required to perform 36 crossmatches and 12 serum antibody specificity determinations. Settings.—Data of participating centers were compared to establish whether EFI requirements were satisfied. Results.—In crossmatch analysis, the results of 32 of 36 crossmatches reached the 75% consensus target, with all the participating laboratories meeting the standards of the EFI. In antibody analysis, only 7 of 17 laboratories met the EFI standards. Conclusion.—The first Italian QC program shows that the participating laboratories obtained consistent results in crossmatching, whereas the results were less satisfactory in the determination of serum antibody specificity, where consensus was reached only with monospecific sera and antibody-negative samples.

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