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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

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Volume 53, Issue 10 (Sep 2015)

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Assessing quality on the Sigma scale from proficiency testing and external quality assessment surveys

James O. Westgard
  • Corresponding author
  • Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI, USA
  • Westgard QC, Inc., Madison, WI, USA
  • Email:
/ Sten A. Westgard
  • Westgard QC, Inc., Madison, WI, USA
Published Online: 2015-02-11 | DOI: https://doi.org/10.1515/cclm-2014-1241

Abstract

Background: There is a need to assess the quality being achieved for laboratory examinations that are being utilized to support evidence-based clinical guidelines. Application of Six Sigma concepts and metrics can provide an objective assessment of the current analytical quality of different examination procedures.

Methods: A “Sigma Proficiency Assessment Chart” can be constructed for data obtained from proficiency testing and external quality assessment surveys to evaluate the observed imprecision and bias of method subgroups and determine quality on the Sigma scale.

Results: Data for hemoglobin A1c (HbA1c) from a 2014 survey by the College of American Pathologists (CAP) demonstrates that approximately two-thirds of the examination subgroups provide only two-Sigma quality when evaluated against the CAP requirement of an allowable total error of 6.0%. The weighted averages were 1.46 Sigma for a survey sample with an assigned value of 6.49% Hb (average bias 2.31%, CV 2.87%), 1.45 Sigma at 6.97% Hb (average bias 2.29%, CV 2.81%), and 1.75 at 9.65% Hb (average bias 1.55%, CV 2.71%). Maximum biases for examination subgroups were 5.7%, 5.8%, and 4.1%, respectively.

Conclusions: Assessment of quality on the Sigma scale provides evidence of the analytical performance that is being achieved relative to requirements for intended use and should be useful for identifying and prioritizing improvements that are needed in the analytical quality of laboratory examinations. In spite of global and national standardization programs, bias is still a critical limitation of current HbA1c examination procedures.

Keywords: external quality assessment; proficiency testing; Sigma quality

References

  • 1.

    Plebani M. The CCLM contribution to improvements in quality and patient safety. Clin Chem Lab Med 2013;51:39–46. [Web of Science]

  • 2.

    Westgard JO. Six Sigma quality design & control, 2nd ed. Madison WI: Westgard QC, Inc., 2006.

  • 3.

    Westgard JO. Basic method validation, 3rd ed. Madison WI: Westgard QC, Inc., 2008.

  • 4.

    Westgard JO. Basic QC practices, 3rd ed. Madison WI: Westgard QC, Inc., 2010.

  • 5.

    Westgard JO. Six Sigma risk analysis. Madison WI: Westgard QC, Inc., 2011.

  • 6.

    Westgard JO, Westgard SA. The quality of laboratory testing today: an assessment of sigma metrics for analytical quality using performance data from proficiency testing surveys and the CLIA criteria for acceptable performance. Am J Clin Pathol 2006;125:343–54.

  • 7.

    Westgard JO, Westgard SA. Basic quality management systems: essentials for quality management in the medical laboratory. Madison WI: Westgard QC, Inc., 2014:234–5.

  • 8.

    NGSP website. Available from: www.ngsp.org. Accessed 1 December, 2014.

  • 9.

    Bruns DE, Boyd JC. Few point-of-care hemoglobin A1c assay methods meet clinical needs. Clin Chem 2010;56:4–6.

  • 10.

    Thienpont LM, Van Utfanghe K, Cabaleiro DR. Metrological traceablity of calibration in the estimation and use of common medical decision-making criteria. Clin Chem Lab Med 2004;42:842–50.

  • 11.

    Magnusson B, Ellison SL. Treatment of uncorrected measurement bias in uncertainty estimation for chemical measurements. Anal Bioanal Chem 2008;390:201–13. [Web of Science]

  • 12.

    Woolworth A, Korpi-Steiner N, Miller JJ, Rao LV, Yundt-Pacheco J, Kuchipudi L, et al. Utilization of assay performance characteristics to estimate Hemoglobin A1c result reliability. Clin Chem 2014;60:1073–9. [Web of Science]

  • 13.

    Lenters-Westra E, Slingerland RJ. Three of 7 hemoglobin A1c point-of-care instruments do not meet generally accepted analytical performance criteria. Clin Chem 2014;60:1062–72.

  • 14.

    Jassam N, Yundt-Pacheco J, Jansen R, Thomas A, Barth JH. Can current analytical quality performance of UK clinical laboratories support evidence-based guidelines for diabetes and ischaemic heart disease? – A pilot study and a proposal. Clin Chem Lab Med 2013;51:1579–84.

About the article

Corresponding author: James O. Westgard, Westgard QC, Inc., 7614 Gray Fox Trail, Madison, WI 53717, USA, Phone: +1 608 833 4718, E-mail: ; and Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI, USA


Received: 2014-12-15

Accepted: 2015-01-16

Published Online: 2015-02-11

Published in Print: 2015-09-01



Citation Information: Clinical Chemistry and Laboratory Medicine (CCLM), ISSN (Online) 1437-4331, ISSN (Print) 1434-6621, DOI: https://doi.org/10.1515/cclm-2014-1241. Export Citation

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