Monitoring of lot changes, delta checks, critical results and reference range

ISO 15189:2022 requires laboratories to have processes in place to identify, assess, and control risks that could lead to patient harm. ISO 22367:2020 expands on this, providing a framework for risk management in medical laboratories, including the need for proactive monitoring of analytical performance. Internal quality control (IQC) is central to daily risk control, but it does not detect all possible failures. In particular, IQC can be limited by the behaviour of control materials, which may not fully reflect how patient samples respond to analytical changes.

Some analytical shifts occur without triggering IQC alarms, yet still affect patient results. Others may cause changes in QC measurements without altering patient outcomes, leading to unnecessary investigations or delays. These limitations mean that laboratories need additional monitoring strategies to identify risks that IQC alone may miss.

This article focuses on external analytical signals – tools and methods that provide an additional layer of monitoring outside routine IQC. These include lot-to-lot verification, delta checks, monitoring the frequency of critical results, and tracking shifts in patient result distributions relative to reference ranges. Each of these signals can reveal different types of risk, and each must be interpreted in the context of the clinical role of the test, the patient population, and the potential consequences of error.