What is a Levey-Jennings chart and how is it used in laboratory QA?

• A. To track patient sample flow through the lab.
• B. To display calibration curves for each instrument.
• C. To plot daily QC results with mean and control limits to detect shifts.
• D. To map reagent shelf-life expiration.

Answer: (C)

A Levey-Jennings chart is a quality assurance tool used in laboratories to monitor how an assay is performing over time by plotting daily QC results against a central mean and control limits. The central line represents the established average of QC values, while the upper and lower control limits show the expected range of normal variation (often set at a defined number of standard deviations from the mean). By charting each QC result, you can quickly see whether the process is stable or if there are shifts, trends, or outliers. If a QC result falls outside the control limits or if a pattern emerges—such as several consecutive points on the same side of the mean or a steady rise or fall—that signals a potential issue with the instrument, reagents, or calibration and should prompt investigation before patient results are affected. This chart is specifically for monitoring QC data over time, not for tracking patient sample flow, displaying calibration curves, or mapping reagent shelf life.