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

Seyda Ozdemir,Fatma Ucar

doi:10.1515/labmed-2021-0116

Abstract

Abstract 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.

Highlights

World Health Organization (WHO) defines the concept of patient safety as “the absence of preventable harm to a patient during the process of health care and reduction of risk of unnecessary harm associated with health care to an acceptable minimum” [1]
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 TEa of each assay was based on five standards: 1) Desirable biological variation (BV) database specifications (BV-EFLM) [18], 2) American Clinical Laboratory Improvement Amendments (New criteria of CLIA) [19], 3) State of Art (SOTA) [20, 21], 4) Standards of

Summary

Introduction

World Health Organization (WHO) defines the concept of patient safety as “the absence of preventable harm to a patient during the process of health care and reduction of risk of unnecessary harm associated with health care to an acceptable minimum” [1]. Regarding patient safety from the past to the present, laboratory medicine has been focused on the risk of negative consequences associated with laboratory tests and their prevention. Clinical laboratories play an essential role in the management of patient, providing important information critical to diagnosis, treatment and monitorization of diseases [2, 3]. From this point of view, it is very important that laboratories produce reliable results by targeting the strict quality assurance program. Despite errors in laboratories are more frequently encountered during pre- and postanalytical processes, analytical errors constitute approximately 10% of total laboratory errors and the consequences negatively affect the patient safety. Comparatively less error rates appear in the analytical phase, it is obvious that the issue of analytical quality is of high importance in terms of determining laboratory errors, and further improvement is supposed to be inevitable in this area [4–6]

Objectives

Results

Conclusion