Prospective real-time implementation and verification of patient-based real-time quality control using average of normals in a tertiary hospital laboratory

OBJECTIVES: Practical implementation of patient-based real-time quality control (PBRTQC) requires analyte- and institution-specific optimization. This study evaluated the operational feasibility of average-of-normals (AoN)-based PBRTQC through a structured selection process and prospective event-based validation. METHODS: Lab Operations (Roche Diagnostics, Mannheim, Germany), which implements a simple moving average (SMA) algorithm. Candidate analytes were selected using retrospective patient results generated on cobas 8,000 series analyzers (Roche Diagnostics, Mannheim, Germany). Analyte selection was guided by a predefined, institution-specific algorithm incorporating distributional stability, biological variability, and operational characteristics. Visit-type stratification was considered when the absolute difference between the overall CV and the mean visit-type-specific CV exceeded 0.5 percentage points. PBRTQC parameters were optimized using a retrospective training dataset and subsequently verified in an independent dataset. Prospective validation was conducted using an event-based framework incorporating patient sample re-measurement and contemporaneous IQC evaluation. RESULTS: Based on the selection algorithm, creatinine, sodium, chloride, potassium, calcium, and free thyroxine were selected, with α-fetoprotein, aspartate aminotransferase, and alanine aminotransferase included for comparison. Across 14 PBRTQC parameter sets, 217,372 AoN points generated 1,599 alarms consolidated into 300 events. Calcium, chloride, creatinine (outpatient), and sodium showed high proportions of meaningful events (38-82 % of total events), whereas AFP and potassium predominantly generated non-confirmatory alarms. CONCLUSIONS: AoN-based PBRTQC can complement conventional IQC for selected analytes. Its performance is strongly dependent on analyte characteristics and institution-specific patient result distributions, underscoring the need for ongoing monitoring and periodic re-evaluation to ensure sustained performance in routine laboratory practice.