Indian journal of Medical Biochemistry

Register      Login

VOLUME 24 , ISSUE 1 ( January-April, 2020 ) > List of Articles

Original Article

Evaluation of Analytical Performance in Clinical Biochemistry Laboratory in India Using Six Sigma Methodology

Nishtha Wadhwa, Anitha Devanath

Keywords : Quality control, Root cause analysis, Six sigma, Total error, Westgard rules

Citation Information : Wadhwa N, Devanath A. Evaluation of Analytical Performance in Clinical Biochemistry Laboratory in India Using Six Sigma Methodology. Indian J Med Biochem 2020; 24 (1):19-24.

DOI: 10.5005/jp-journals-10054-0131

License: CC BY-NC 4.0

Published Online: 22-08-2020

Copyright Statement:  Copyright © 2020; Jaypee Brothers Medical Publishers (P) Ltd.


Introduction: Internal and external quality controls (QCs) used in the laboratory are effective in detecting analytical errors. However, they cannot quantify the number of errors. Six sigma can be used to objectively evaluate the performance of analytical methods. Hence, we have evaluated the analytical performance of 19 parameters using six sigma methodology. Materials and methods: Quality control data were collected over a period of 6 months—from January to June 2016—and sigma metric was calculated. Parameters showing sigma metrics of ≤3 were further analyzed between July and September 2016 by applying the suggested rules from Unity Real Time (URT) software. Results: Gamma-glutamyl transferase (GGT) Level (L) 2 showed the highest value of sigma (13.22). Total bilirubin was found to have the highest sigma values at both control levels (7.15 and 9.49 at L1 and L2, respectively). Sigma value of ≥4 was observed across all control levels for anti-TPO, CK-MB, potassium, PSA, and TSH. L1 of alpha feto protein (AFP) and L2 of Troponin I had sigma value of ≤3. We have obtained sigma value of ≤3 for all levels of remaining analytes. Among these, L1 of AFP showed a significant improvement in sigma after the application of suggested rules (2.5 to 9.3). Conclusion: The sigma value for a test is a good indication of its process capability because it considers both bias and imprecision. Unfortunately, most clinical laboratory tests are below six sigma processes. It is imperative to implement appropriate QC strategies for the judicious use of quality control.

PDF Share
  1. Cooper G. Basic Lessons in Laboratory Quality Control. Bio-Rad Laboratories, Inc.; 2008.
  2. Cooper G, De Jonge N, Ehrmeyer S. Collective opinion paper on findings of 2010 convocation of experts on laboratory quality. Clin Chem Lab Med 2011;49(5):793–802. DOI: 10.1515/CCLM.2011.149.
  3. Westgard S. Prioritizing risk analysis quality control Plans based on Sigma-metrics. Clin Lab Med [Internet] 2013;33(1):41–53. DOI: 10.1016/j.cll.2012.11.008.
  4. Westgard Sigma Rules [Internet]. [cited 2018 Dec 12]. Available from:
  5. Perich C, Minchinela J, Ricós C, et al. Biological variation database: Structure and criteria used for generation and update. Clin Chem Lab Med 2015;53(2):299–305. DOI: 10.1515/cclm-2014-0739.
  6. Westgard JO. Basic QC. Practices 2010. 312.
  7. Nanda SK, Ray L. Quantitative application of sigma metrics in medical biochemistry. J Clin Diagnostic Res 2013;7(12):2689–2691. DOI: 10.7860/JCDR/2013/7292.3700.
  8. Singh B, Goswami B, Gupta VK, et al. Application of sigma metrics for the assessment of quality assurance in clinical biochemistry laboratory in India: a pilot study. Indian J Clin Biochem 2011;26(2): 131–135. DOI: 10.1007/s12291-010-0083-1.
  9. Kumar BV, Mohan T. Sigma metrics as a tool for evaluating the performance of internal quality control in a clinical chemistry laboratory. J Lab Physicians 2019;10(2):194–199. DOI: 10.4103/JLP.JLP_102_17.
  10. Iqbal S, Mustansar T. Application of sigma metrics analysis for the assessment and modification of quality control program in the clinical chemistry laboratory of a tertiary care hospital. Indian J Clin Biochem 2017;32(1):106–109. DOI: 10.1007/s12291-016-0565-x.
  11. Hens K, Berth M, Armbruster D, et al. Sigma metrics used to assess analytical quality of clinical chemistry assays: importance of the allowable total error (TEa) target. Clin Chem Lab Med 2014(7): 973–980. DOI: 10.1515/cclm-2013-1090.
  12. Westgard JO, Burnett RW. Precision requirements for cost-effective operation of analytical processes. Clin Chem 1990;36(9):1629–1632. DOI: 10.1093/clinchem/36.9.1629.
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.