Background: Sigma metrics (σ) guide risk-based quality control (QC) by integrating bias, imprecision and TEa. We summarize how two analyzers maintained their Sigma bands over time and where analytes moved up a band, following targeted QC interventions. Methods: Average σ was compiled at QC levels (L1/L2/L3 wherever is applicable) and categorized into >6 sigma,>5 to4 to 3 to 5 σ for Clinical Chemistry (50.0%→73.1%). Instrument 56000582 (backup) showed improved >5 σ share in Immunoassay (57.1%→71.4%), with Prolactin moving up into ≥5 σ while other analytes maintained high bands.
Conclusions: Enhanced QC preparation/handling/storage, calibration, and lot management supported maintenance within bands sustained Sigma performance and band-up improvements without emphasizing declines.