A Levey-Jennings chart puts each Control result, run by run, against its mean and lines at ±1, ±2 and ±3 SD. Use the mean and SD your laboratory set for that Control lot (or the insert's, until you have your own).
| Rule | When it fires | Usually means |
|---|---|---|
| 1-2s | one result beyond ±2 SD | a warning: look at the other rules before releasing |
| 1-3s | one result beyond ±3 SD | reject the run: random error |
| 2-2s | two results in a row beyond 2 SD on the same side | reject: systematic error |
| R-4s | two results in one run more than 4 SD apart | reject: random error |
| 4-1s | four results in a row beyond 1 SD on the same side | reject: a shift |
| 10x | ten results in a row on the same side of the mean | reject: a shift or a trend |
When a run is rejected
- Hold the patient results of that run.
- Check the Control itself: lot, expiry, how it was stored and reconstituted, a new Control lot opened recently.
- Check the reagent: lot, expiry, days on board, the opened date in My stock.
- Recalibrate if the IFU asks for it or if every level moved the same way.
- Rerun the Controls. Still out? Report a problem with the runs and the last calibration.