Quality control frequency: Unleashing the truth.

Objectives: This study investigates the optimal number of quality control (QC) events per day in two scenarios: high-sensitive troponin, requiring three levels of QC materials, and creatinine, with two levels. The aim is to explore how different QC rules and sigma metric values affect the frequency of QC events, considering both analytical performance and the clinical impact of potential measurement errors as severity of harm.

Methods: Risk-based QC calculations were performed using the QC Constellation tool. Four QC rule schemes (1-3 s, 1-3 s/2-2 s, 1-3 s/2-2 s/R-4 s, 1-3 s/2-2 s/R-4 s/4-1 s) were tested for high-sensitive troponin (catastrophic harm) and creatinine (serious harm). Sigma metric values from 3 to 6 were evaluated to determine maximum run sizes. QC event frequency was estimated for a hypothetical laboratory processing 1,000 samples daily.

Results: Maximum run sizes decreased as sigma metric values declined. Correspondingly, the number of QC events per day increased as sigma metric values decreased. For high-sensitive troponin, with its catastrophic severity of harm related to potantial error, more frequent QC was necessary compared to creatinine.

Conclusions: Analytical performance and severity of harm significantly influence the required frequency of QC events. Laboratories must consider both factors when designing QC strategies to balance patient safety with operational efficiency. For analytes with high severity of harm, achieving higher sigma metrics is critical to maintain feasible and cost-effective QC practices. A hybrid QC approach combining risk-based and patient-based methods may optimize QC strategies, but standardization of sigma metric calculations is still needed.