Application and insights on patient-based real-time quality control: detecting undetected errors in internal quality control through daily antibody positivity rate analysis.

Introduction: Traditional internal quality control (IQC) has limitations in detecting systematic errors in clinical laboratories. Patient-Based Real-Time Quality Control (PBRTQC) has emerged as a complementary method, offering new approaches for quality monitoring. Among these, monitoring daily positivity rates provides meaningful insights into laboratory performance.

Materials and methods: This study highlights a case in which PBRTQC was implemented to detect and address a reagent batch issue in thyroid peroxidase antibody (TPO-Ab) testing. Over one year (July 2023 to July 2024), daily positivity rates and their fluctuations were retrospectively analyzed and daily positivity rate alarm limits were established for monitoring.

Results: A notable increase in the TPO-Ab positivity rate was identified starting in June 2024. For outpatients and inpatients, the positivity rates in June and July 2024 were 46.1% ± 7.8% (N = 9039) and 61.4% ± 12.0% (N = 8735), respectively. For the physical examination population, the positivity rates during the same months were 30.0% ± 11.7% (N = 4754) and 52.5% ± 18.1% (N = 5726), respectively. These rates were significantly higher than the pre-June 2024 average monthly positivity rates of 30.0% ± 2.9% (N = 9070 per month) for patients and 11.0% ± 2.4% (N = 4663 per month) for the physical examination population.

Conclusions: PBRTQC, particularly monitoring daily positivity rates, is a valuable tool for early detection of systematic errors. Establishing PBRTQC systems can supplement traditional IQC to improve laboratory test quality.