Comparison between Sigma metrics in four accredited Egyptian medical laboratories in some biochemical tests: an initiative towards sigma calculation harmonization

Abstract

IntroductionAnalytical quality is an essential requirement for best practice in any medical laboratory. Lack of a harmonized approach for sigma calculation is considered an obstacle in the objective comparability of analytical performance among laboratories adopting sigma metrics. It is urgently needed that all laboratory professionals interested in the analytical quality to work hard towards harmonization protocol for sigma calculation in order to properly select their analytical goals. This study aims at harmonization of Sigma metrics calculation in four accredited Egyptian laboratories.Materials and methodsThis observational cross sectional study compared the sigma levels for certain biochemical parameters in the four participating laboratories.ResultsCoefficient of variation (CV) and bias were determined for some biochemical analytes, data assayed by different automated analysers in the four different accredited laboratories. The sigma level for the four medical laboratories was calculated for each biomedical parameter with changed sigma level after total allowable error (Tea) unification among participating laboratories.ConclusionEach laboratory should select the TEa goal based on clear standardized criteria of selection without any subjective preferences as either under or over estimation of Sigma metrics will affect the patient centred care negatively if laboratories use quality control procedures wrongly based on incorrect Sigma metrics calculation with subsequent misleading medical decisions.

Comparative analysis of calculating sigma metrics by a trueness verification proficiency testing‐based approach and an internal quality control data inter‐laboratory comparison‐based approach

“…21 It provides a feasible model for standardizing protocols and is being introduced to encourage all laboratories to use the same quality goals for their sigma metrics benchmarks. 22 Because TEa WS/T was more stringent than TEa CLIA for the most analytes, the σ WS/T was significantly lower than that of σ CLIA in 18 out of 19 assays (all except Na). Therefore, the limitation of selecting an appropriate TEa requirement for σ calculation should be considered.…”

Sigma Metrics Assessment as Quality Improvement Methodology in a Clinical Chemistry Laboratory

“…If CV is less than 5%, then the particular method used for determination of an analyte’s concentration is said to have a very good performance& precise. 7,10,13 It can be visualised from Table1 & Table 2 that except for HDL, (CV%>5 in both L 1 & L 2 ) along with Total bilirubin & ALT (having CV%>5 in L 1 ); rest all parameters depicted CV<5%. This clearly indicates that our lab has achieved high level of precision in remaining 11 analytes.…”

Application of the sigma metrics to evaluate the analytical performance of cystatin C and design a quality control strategy

“…The sigma symbol represents the ‘standard deviation’ in mathematical statistics, and its value usually reflects the testing quality level. 17 Six sigma represents a ‘world-class’ quality level, indicating that for every one million products (or services), only 3.4 defects can be detected, which is the expected quality goal. 17 The calculation of sigma depends on three variables: TEa, precision and accuracy.…”

“…17 Six sigma represents a ‘world-class’ quality level, indicating that for every one million products (or services), only 3.4 defects can be detected, which is the expected quality goal. 17 The calculation of sigma depends on three variables: TEa, precision and accuracy. TEa represents the quality goals selected by the laboratory, and previous studies have shown that there are significant differences in sigma levels for the quality goals used for the same analytes in the same laboratories.…”