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QC Failure Investigation Checklist
The order I've taught new techs for years. It won't replace your SOP, but it'll stop anyone reaching for "just rerun it".
1
Stop and protect patients
- Stop reporting this test on this instrument
- Hold patient results from the failed run
- Tell the charge tech or supervisor; move stats to a backup if you have one
- Look at the Levey-Jennings chart, not just today's point
2
Read the pattern
| 1-2s | Warning only. Check the other rules and the chart before rejecting (unless your lab uses it to reject). |
| 1-3s · R-4s | Think random error first: bubble, clot, short sample, probe, mixing, a bad vial. |
| 2-2s · 4-1s · 10x | Think systematic error first: calibration, reagent or calibrator lot, drift, ageing lamp or electrode. |
| One level only | Suspect that control vial. If only the high or low level, also consider calibration at the ends of the range. |
| All levels, same way | Common cause: reagent, calibration, instrument. |
3
Control material
- Right control, right level, right position
- Reconstituted correctly: diluent, volume, mixing, wait
- Within open-vial stability and expiry
- Stored and thawed properly
- Not evaporated (cap off, left on board)
- Try a fresh vial
4
Reagent
- Lot changed recently?
- On-board stability not exceeded
- No bubbles, precipitate, contamination
- Stored correctly before loading
- Try a fresh pack
5
Calibration
- When was it last calibrated?
- Calibrator lot, reconstitution, expiry
- Compare curve or factor with the last good one
- Recalibrate if indicated, then run all QC levels
6
Instrument & environment
- Flags, alarms, error messages
- Maintenance up to date
- Probes, mixers, wash, cuvettes, lamp, electrodes
- Reaction temperature, room temperature, water
- Other tests on this analyser affected too?
7
Fix, verify, look back, document
- Correct the cause and run all QC levels. Resume only when acceptable
- Find the last acceptable QC; rerun selected patients from that window
- If reruns differ beyond your allowable limit, follow your corrected-report procedure and notify
- Document: what failed, what you checked, root cause, action, repeat QC, look-back, who you told
- Hand it to your supervisor for review
Never rerun controls until they pass.One repeat with fresh control can be reasonable for suspected random error if your SOP allows it. Anything beyond that is hiding a problem.
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