Concentration-specific Integrated Evaluation of Analytical Performance Using Sigma Metrics and Measurement Uncertainty in Clinical Chemistry

This single-center study evaluated 36 clinical chemistry analytes at low/high internal quality control (IQC) levels by integrating the sigma values and approximate expanded uncertainty (U).The sigma values were calculated from the total allowable error (TEa), the six-month IQC coefficient of variation (CV 6-month ), and external quality assessment (EQA) bias.U was approximated from CV 6-month and the absolute EQA bias using a coverage factor of k=2; the U/TEa ratios expressed U relative to TEa.Low/high IQC comparisons and associations used the Wilcoxon signed-rank and Spearman tests, respectively.At low/ high IQC levels, 72.2% and 83.3% of analytes showed excellent performance, respectively.High-level IQC had higher sigma values (P<0.001) but lower U (P=0.005) and U/TEa ratios (P<0.001).Low-level creatinine was the only analyte with U/TEa ≥1.Six analytes (16.7%) shifted to better integrated performance categories at the high level, with none shifting to poorer categories.The CV-related components predominated in 63.9% and 80.6% of analytes, respectively, and predominant component classification changed between levels in 10 analytes (27.8%).The sigma values were strongly negatively correlated with U/TEa at both levels (ρ=-0.88,P<0.001), reflecting their shared calculation structure.This exploratory framework may identify concentration-dependent performance differences and prioritize analytes and error components for further review.