Introduced in 1950 by pathologists Stanley Levey and E. R. Jennings , the chart adapted Walter Shewhart’s industrial process control methods for the medical lab. Before this, labs often relied on double measurements to ensure precision; the LJ chart revolutionized the field by providing a structured, visual way to track analytical stability. Interpreting the Chart with Westgard Rules
The L-J chart serves as the visual map where these rules are applied. It allows lab personnel to distinguish between a simple statistical fluke and a genuine mechanical failure. levy jenning chart
While the chart provides the visual data, Westgard Rules provide the logic for interpretation. These multirule procedures help labs decide if a test run should be accepted or rejected: Introduced in 1950 by pathologists Stanley Levey and E
❌ – A chart without rule-checking is just a line. ❌ Using the same SD for months – Recalculate mean and SD every 3–6 months or after major maintenance. ❌ Ignoring shifts/trends – A slow drift may not violate ±3s for weeks, but it still biases results. ❌ Failing to document actions – Always note what you found and fixed when a rule is broken. Before this, labs often relied on double measurements