A Pilot Study on the Evaluation of Clinical Chemistry Laboratory Test Performance using Six Sigma Metrics


  • Pier Angeli Medina The Medical City
  • Jenny Matibag The Medical City
  • Sarah Jane Datay-Lim The Medical City
  • Elizabeth Arcellana-Nuqui The Medical City




bias, laboratory, quality control, quality improvement, six sigma, Westgard rules


Introduction Six sigma has been used over the years, initially in manufacturing industries to improve quality by reducing the number of wastes and defects. In the laboratory, it can also provide measurement of quality using the sigma scale.

Objectives The main objective of the study is to evaluate the performance of tests in two chemistry analyzers using the six sigma scale.

Methodology A total of twenty (28) tests were evaluated on two Abbott Architect c8000 chemistry analyzers from September 2014 to July 2019 using results of quality control mean, coefficient of variation, bias and total allowable error to compute for the six sigma value. Both level one and level two third party quality controls were included in the evaluation.

ResultsOResults of the study showed the tests that were >6 sigma for both levels 1 and 2 throughout the 5 years. Di-Bil, CK, HLD, TG and UA were consistently >6 sigma for one machine while CK, Di-Bil, HDL, Mg, TG and UA were consistently >6 sigma for the other. Level 1 and Level 2 sigma scores were noted to be incongruent in some analytes as follows: ALB, ALT, K, TP for one instrument and ALB, ALP and AST for the other instrument. Electrolytes Ca, Cl, and Na were generally low (

Conclusion Using six sigma metrics allowed the laboratory to evaluate the performance of the chemistry tests objectively. Tests that are >6.0 sigma signifies world class performance and entail application of fewer Westgard rules with fewer number of runs while those that are


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Author Biographies

Pier Angeli Medina, The Medical City


Jenny Matibag, The Medical City

Quality Officer

Sarah Jane Datay-Lim, The Medical City

Laboratory Quality and Saftey Consultant Director

Elizabeth Arcellana-Nuqui, The Medical City

Consultant Director for Chemistry and Immunology

Department Chair


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

2. Westgard JO. Six sigma quality design and control. Madison, WI. Westgard QC, Inc., 2006.

3. Lippi G, Plebani M. A six-sigma approach for comparing diagnostic errors in healthcare- where does laboratory medicine stand? Ann Transl Med. 2018;6(10):180. https://pubmed.ncbi.nlm.nih.gov/29951502. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5994534. https://doi.org/10.21037/atm.2018.04.02.

4. Singh B, Goswami B, Gupta VK, Chawla R, Mallika V. Application of sigma metrics for the assessment of quality assurance in clinical biochemistry laboratory in India: a pilot study. Ind J Clin Biochem. 2011;26(2):131-5. https://pubmed.ncbi.nlm.nih.gov/22468038. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3107403. https://doi.org/10.1007/s12291-010-0083-1.

5. Chaudhary NG, Patani SS, Sharma H, Maheshwari A, Jadhav PM, Maniar MA. Application of six sigma for the quality assurance in clinical biochemistry laboratory – a retrospective study. Int J Res Med. 2013:2(3):17-20.

6. Lakshman M, Reddy BR, Bhulaxmi P, et al. Evaluation of sigma metrics in a Medical Biochemistry lab. Int J Biomed Res. 2015;6(3):164-71. https://doi.org/10.7439/ijbr.

7. Modi N, Shah T. Application of six sigma test in clinical biochemistry laboratory. Int J Res Med. 2017;6(2):75-8.

8. CLIA Requirements for Analytical Quality. https://www.westgard.com/clia.htm.

9. Ricós C, Alvarez V, Cava R et.al. Current databases on biological variation: pros, cons and progress. Scand J Clin Lab Invest. 1999;59(7):491-500. https://pubmed.ncbi.nlm.nih.gov/10667686. https://doi.org/10.1080/00365519950185229.

10. Friedecky B, Kratochvila J, Budina M. Why do different EQA schemes have apparently different limits of acceptability? Clin Chem Lab Med. 2011;49:743-5. https://pubmed.ncbi.nlm.nih.gov/21235390. https://doi.org/10.1515/CCLM.2011.105.

11. Hens, K, Berth M, Armbruster D, Westgard S. Sigma metrics used to assess analytical quality of clinical chemistry assays: importance of the allowable total error (TEa) target. Clin Chem Lab Med 2014;52(7):973-80. https://pubmed.ncbi.nlm.nih.gov/24615486. https://doi.org/10.1515/cclm-2013-1090.

12. Guo X, Zhang T, Gao X, et al. Sigma metrics for assessing the analytical quality of clinical chemistry assays: a comparison of two approaches: electronic supplementary material available online for this article. Biochem Med (Zagreb). 2018;28(2):
020708. https://pubmed.ncbi.nlm.nih.gov/30022883. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039159. https://doi.org/10.11613/BM.2018.020708.




How to Cite

Medina, P. A., Matibag, J., Datay-Lim, S. J., & Arcellana-Nuqui, E. (2019). A Pilot Study on the Evaluation of Clinical Chemistry Laboratory Test Performance using Six Sigma Metrics. PJP, 4(2), 31–36. https://doi.org/10.21141/PJP.2019.13



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