Jump to ContentJump to Main Navigation
Show Summary Details
More options …

Clinical Chemistry and Laboratory Medicine (CCLM)

Published in Association with the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM)

Editor-in-Chief: Plebani, Mario

Ed. by Gillery, Philippe / Greaves, Ronda / Lackner, Karl J. / Lippi, Giuseppe / Melichar, Bohuslav / Payne, Deborah A. / Schlattmann, Peter

IMPACT FACTOR 2018: 3.638

CiteScore 2018: 2.44

SCImago Journal Rank (SJR) 2018: 1.191
Source Normalized Impact per Paper (SNIP) 2018: 1.205

See all formats and pricing
More options …
Volume 40, Issue 6


Internal Quality Control System for Non-Stationary, Non-Ergodic Analytical Processes Based upon Exponentially Weighted Estimation of Process Means and Process Standard Deviation

Rob T.P. Jansen / Mark Laeven / Wim Kardol
Published Online: 2005-06-01 | DOI: https://doi.org/10.1515/CCLM.2002.107


The analytical processes in clinical laboratories should be considered to be non-stationary, non-ergodic and probably non-stochastic processes. Both the process mean and the process standard deviation vary. The variation can be different at different levels of concentration. This behavior is shown in five examples of different analytical systems: alkaline phosphatase on the Hitachi 911 analyzer (Roche), vitamin B12 on the Access analyzer (Beckman), prothrombin time and activated partial thromboplastin time on the STA Compact analyzer (Roche) and pO2 on the ABL 520 analyzer (Radiometer). A model is proposed to assess the status of a process. An exponentially weighted moving average and standard deviation was used to estimate process mean and standard deviation. Process means were estimated overall and for each control level. The process standard deviation was estimated in terms of withinrun standard deviation. Limits were defined in accordance with state of the art-or biological variancederived cut-offs. The examples given are real, not simulated, data. Individual control sample results were normalized to a target value and target standard deviation. The normalized values were used in the exponentially weighted algorithm. The weighting factor was based on a process time constant, which was estimated from the period between two calibration or maintenance procedures. The proposed system was compared with Westgard rules. The Westgard rules perform well, despite the underlying presumption of ergodicity. This is mainly caused by the introduction of the starting rule of 12s, which proves essential to prevent a large number of rule violations. The probability of reporting a test result with an analytical error that exceeds the total allowable error was calculated for the proposed system as well as for the Westgard rules. The proposed method performed better.

The proposed algorithm was implemented in a computer program running on computers to which the analyzers were linked on-line. Each result was evaluated on-line, and a limit violation was immediately reported. The system has performed satisfactorily in our laboratory for ten analyzers for over 1 year.

About the article

Published Online: 2005-06-01

Published in Print: 2002-06-21

Citation Information: Clinical Chemistry and Laboratory Medicine, Volume 40, Issue 6, Pages 616–624, ISSN (Print) 1434-6621, DOI: https://doi.org/10.1515/CCLM.2002.107.

Export Citation

Citing Articles

Here you can find all Crossref-listed publications in which this article is cited. If you would like to receive automatic email messages as soon as this article is cited in other publications, simply activate the “Citation Alert” on the top of this page.

Graham R. Lee, Maria C. Fitzgibbon, and Paula O'Shea
International Journal of Health Care Quality Assurance, 2016, Volume 29, Number 5, Page 492
Panagiotis Tsiamyrtzis, Frédéric Sobas, and Claude Négrier
Blood Coagulation & Fibrinolysis, 2015, Volume 26, Number 5, Page 590
Tomasz Grabowski, Jerzy Jan Jaroszewski, Walerian Piotrowski, and Małgorzta Sasinowska-Motyl
European Journal of Drug Metabolism and Pharmacokinetics, 2014, Volume 39, Number 2, Page 111
John H. Livesey
Clinical Chemistry and Laboratory Medicine (CCLM), 2005, Volume 43, Number 11
Christophe Nougier, Frédéric Sobas, Thi K Nguyen, Marie L Carage, Anne Lienhart, and Claude Négrier
Blood Coagulation & Fibrinolysis, 2011, Volume 22, Number 2, Page 151
Frédéric Sobas, Audrey Bellisario, Panagiotis Tsiamyrtzis, Anne Lienhart, Christophe Nougier, and Claude Négrier
Blood Coagulation & Fibrinolysis, 2010, Volume 21, Number 3, Page 289

Comments (0)

Please log in or register to comment.
Log in