Analytical performance evaluation of sensitive and old generation reagent in routine practical use: estradiol experience.

Evaluation of the analytical performance of tests in medical laboratories is important. Total Error (TE) and sigma analysis have been used as a quantitative indicator of quality for many years. The aim of this study is to evaluate the analytical performance of Beckman Coulter Access Estradiol (E2) and Sensitive E2 reagents. Analytical performance of two reagents were evaluated with TE, six sigma and measurement uncertainty values. Two Beckman Coulter Unicel DxI-800 autoanalyzers (A1 and A2) included in the study. Quality control data between December 2017 and December 2019 were used. CLIA-2019 values were used for total allowable error (TEa) limits. Uncertainty values were calculated with ISO/TS 20914. The median TE of the old generation and sensitive E2 reagent were 27.46% (between 13.49 and 48.88) and 11.16% (between 7.08 and 24.81), respectively (p < .005) The process sigma results were below 3 sigma in all months with the old reagent, whereas with the new reagents it was seen to be above 3 sigma in 11 of 12 months for both autoanalyzers. Uncertainty of old reagent is higher than new reagent. Imprecisions decrease as concentration increases with both reagents. The uncertainty values of low concentration levels are greater than high concentration levels. In conclusion, in both auto analyzers, Sensitive E2 reagent was found to have better performance than old reagent in terms of TE, process sigma and measurement uncertainty. We believe that the sensitive E2 reagent still needs further improvement for patients who have low E2 levels.

Reference change value and measurement uncertainty in the evaluation of tumor markers.

The use of measurement uncertainty among clinical laboratories becomes widespread. Measurement uncertainty can be reported with the result, as well as be used in certain reference change value (RCV) calculation equations. RCV is especially recommended for use in tests with a low individuality index. In our study, we calculated the measurement uncertainty of AFP, CA 125, CA 15-3, CA 19-9, CEA tumor markers with the ISO TS 20914:2019. We compared results with limits. Two Beckman Coulter DXI-800 (Minnesota, USA) autoanalysers' results were used. We calculated the RCV values using the classical Fraser method, logarithmic Lund Method, and Clinical Laboratory Standards Institute (CLSI) method as Minimal Difference (MD). We found the same permissible measurement uncertainty limit as 15.97% for all five tumor markers. The highest RCV value was found as 90% upstream for AFP test with Lund logarithmic approach, the lowest RCV value was found as 12% for CEA with MD, all other RCV results were between these two values. We do not recommend the use of MD, as values for Biological variation are not used in the MD approach. We also recommend using the logarithmic approach, although it gives higher results. There are also clinical studies on the significance of tumor markers in a follow-up that show different results. These differences may be because the studies are conducted with different systems. Therefore, each laboratory needs to calculate its own RCV values. We also recommend informing the clinicians about the tests with high measurement uncertainty.