Determination of Sigma metric based on various TEa sources for CBC parameters: the need for Sigma metrics harmonization

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Ozdemir S., Ucar F.

Journal of Laboratory Medicine, vol.46, no.2, pp.133-141, 2022 (Scopus) identifier

  • Publication Type: Article / Article
  • Volume: 46 Issue: 2
  • Publication Date: 2022
  • Doi Number: 10.1515/labmed-2021-0116
  • Journal Name: Journal of Laboratory Medicine
  • Journal Indexes: Scopus
  • Page Numbers: pp.133-141
  • Keywords: biological variation, hematology (complete blood count), Sigma metric, total allowable error
  • Ankara Yıldırım Beyazıt University Affiliated: No


© 2022 Seyda Ozdemir and Fatma Ucar, published by De Gruyter, Berlin/Boston.Objectives: The application of Sigma metrics can be used for assessing the performance of diagnostic laboratories. Clinical laboratories are confronted with the trouble of having to select the best and suitable quality specifications that are required for quality planning. In this regard, our study aims at evaluating the performance of Sysmex XN-1000 hematology analyzer by using Sigma metrics based on different total allowable error (TEa) source and to determine the effects of these variations in Sigma metric evaluation. Methods: Five TEa requirements were selected to calculate Sigma metrics of 11 complete blood count (CBC) parameters. Coefficient of variation (CV) and bias data were supplied from internal quality control (IQC) and External Quality Assessment Scheme (EQAS) respectively. Results: According to TEa based on desirable biological variation (BV) database specifications, the highest Sigma value was achieved by white blood cell count for each level, the lowest value was achieved by Red Cell Distribution Width-Standard Deviation parameter. The Sigma calculation based on Spanish TEa showed that seven CBC parameter achieved Sigma value ≥3. Conclusions: According to the results of the study, it can be concluded that Sigma scores have a significant fluctuation based on which TEa sources are utilized and the need for Sigma metrics harmonization and standardization is highlighted. Additionally, low Sigma values of most CBC parameters are resulted in the conclusion that the use of performance goals depending on BV data is difficult for common clinical use. Therefore, clear standardized criteria are quite necessary for the selection of TEa goal by laboratories.