Evaluation of measurement uncertainty of 11 serum proteins measured by immunoturbidimetric methods according to ISO/TS 20914: a 1-year laboratory data analysis.

Abstract

Objectives: Measurement uncertainty (MU) plays an important role in the interpretation of laboratory results, but data on serum proteins analyzed by immunoturbidimetry according to ISO/TS 20914 are limited.

Methods: MU of 11 serum proteins, including CRP, RF, ASO, IgG, IgA, IgM, C3, C4, ceruloplasmin, transferrin, and β2-microglobulin, were estimated using 1-year internal quality control (IQC) data obtained from Roche Cobas analyzers. MU was calculated using uncertainty and calibrator uncertainty according to ISO/TS 20914, assuming negligible deviation from external quality assessment data. Analytical performance specification (APS) models were selected according to the EFLM APS selection criteria, and maximum allowable uncertainty (MAU) values were determined based on sources such as EFLM models and literature.

Results: IgA and RF were the only two analytes that met the required and minimum MAU values, respectively, at both IQC levels. MU values for CRP, ceruloplasmin, transferrin, and β2-microglobulin exceeded targets at both levels. MU for C3, C4, IgG, and IgM exceeded the minimum MAU at IQC1 but remained acceptable at IQC2. MU values for ASO were calculated as 10.01 and 7.22 % but could not be evaluated due to a lack of reference data. Assay precision should be improved for CRP, IgG, IgM, ceruloplasmin, transferrin, and β2-microglobulin. Use of updated calibration materials for CRP may help reduce MU.

Conclusions: Maintaining acceptable precision over a long period remains a challenge for serum proteins analyzed by immunoturbidimetry, highlighting the need for methodological improvements and stricter quality monitoring. In this context, MU assessment is crucial.