Sigma metrics in laboratory medicine revisited: We are on the right road with the wrong map

Oosterhuis W. P. , COŞKUN A.

BIOCHEMIA MEDICA, vol.28, no.2, 2018 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Review
  • Volume: 28 Issue: 2
  • Publication Date: 2018
  • Doi Number: 10.11613/bm.2018.020503
  • Journal Name: BIOCHEMIA MEDICA
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED)
  • Keywords: biological variation, Six Sigma, Sigma metrics, total error, number of distinct categories, CLINICAL-CHEMISTRY, EUROPEAN FEDERATION, ERROR, PERFORMANCE, PROJECT, HEALTHY
  • Acibadem Mehmet Ali Aydinlar University Affiliated: Yes


Reliable procedures are needed to quantify the performance of instruments and methods in order to increase the quality in clinical laboratories. The Sigma metrics serves that purpose, and in the present study, the current methods for the calculation of the Sigma metrics are critically evaluated. Although the conventional model based on permissible (or allowable) total error is widely used, it has been shown to be flawed. An alternative method is proposed based on the within-subject biological variation. This model is conceptually similar to the model used in industry to quantify measurement performance, based on the concept of the number of distinct categories and consistent with the Six Sigma methodology. The quality of data produced in clinical laboratories is expected, however, to be higher than the quality of industrial products.