Debrief: what the chart supports and what it does not

The chart supports naming a pattern (here, a shift shared across two control levels), identifying the first date the evidence changed (Aug 6), and pointing you to the most relevant record given that timing (the lot-bridging comparison and related transition records). That is what a Levey-Jennings chart is for: it is monitoring evidence built on the expectation that, for a stable process, about 95.45 percent of results fall within plus or minus 2 SD and about 99.73 percent within plus or minus 3 SD, so a sustained departure from that expectation is worth a look.

The chart does not, by itself, prove that the reagent lot caused the shift. It does not replace the documented bridging study, calibration check, or event log entry that actually establishes cause. Statistical quality control does not detect every specimen-specific or preexamination error, so acceptable controls do not prove that every patient result from a run is free of error; the chart and the specimen-level checks answer different questions.

Everything about point counts for a shift or trend, warning versus action rules, the exact lot-bridging protocol, and the required response sequence is local policy, not a universal number. This chart used generic mean and SD lines and a generic pattern vocabulary; your laboratory's approved QC rule set and procedure are the actual reference when you are back at the bench. A quality-control plan is specific to the measuring system, laboratory environment, and clinical application in use, and its effectiveness is monitored after it is implemented.

These values are QC targets for control material, not reference intervals. Read the chart for the pattern and timing, then let the documented event and bridging records, not the chart alone, carry the conclusion.