Long time monitoring of serum lithium results using patient median values show stable test results over a time period of more than 20 years

Abstract

Introduction and Objectives

Internal and external quality assurance materials often rely on highly processed matrices, which can compromise their commutability. As a result, they may not fully reflect the behavior of actual patient samples across different analytical systems. Monitoring laboratory methods using patient median values provides a complementary tool for identifying and correcting systematic errors that could otherwise impact diagnostic accuracy. The aim of the present study was to evaluate the utility of median patient lithium results in monitoring method performance over time.

Materials and Methods

Patient lithium results from 2004 to 2024 were analyzed (n = 64848) to assess long-term trends and seasonal variation. Lithium measurements were initially performed using an Abbott Architect instrument and were later transferred to a Roche Cobas Pro platform.

Results

Patient median and quartile values showed that lithium had a stable calibration between 2004 and 2024. The lithium results did not show seasonal variation.

Conclusions

Monitoring lithium tests using patient medians, and quartiles offers a robust and clinically relevant addition to traditional internal and external quality controls for method monitoring.