Overview
A QC failure occurs when a control result falls outside its acceptable range, meaning the testing system has not demonstrated it is working correctly for that analyte at that time. It is a signal to stop and investigate, not a paperwork item to resolve later.
Classification
| Decision checkpoint | Action |
|---|---|
| Any control level out of range | Hold patient testing for that analyte |
| Cause not yet identified | Do not resume, investigate first |
| Corrective action applied | Rerun QC before touching patient samples |
| QC confirmed within range | Resume testing and document the timeline |
| Results already run since last valid QC | Review and hold release pending investigation |
Morphologic Features
Not applicable, this entry covers a laboratory process decision, not cell or specimen morphology.
Laboratory Characteristics
- Failure can be isolated to one control level or affect the whole panel
- Common causes: control material, reagent lot, calibration drift, instrument fault, technique
- A partial failure (one level out, one in) still means the run is unverified
Reference Intervals
Not applicable as a patient reference interval. QC acceptable ranges are analyzer- and lot-specific and defined by the local laboratory procedure and control manufacturer.
Clinical and Laboratory Significance
A QC failure has no direct patient diagnostic meaning by itself, its significance is that any patient result generated under a failed or unverified system cannot yet be trusted for clinical decision-making.
Differential Considerations
Distinguish a true system problem (reagent, calibration, instrument fault) from a control-handling error (expired, contaminated, or mis-reconstituted control) and from a one-off technique slip during the QC run itself, the investigation approach differs for each.
Comparison Tables
QC failure checkpoints
| Pressure point | Safe response | Unsafe shortcut |
|---|---|---|
| Samples already waiting | Hold testing until QC is resolved | Run patients now, sort QC out later |
| Urgent request pending | Investigate quickly; communicate the delay | Skip investigation because it is urgent |
| Cause unclear | Work through control, reagent, calibration, instrument systematically | Rerun QC repeatedly hoping it passes |
Classification Frameworks
Not applicable . WHO disease classifications do not define laboratory QC failure response.
Laboratory Notes
- Hold → investigate → correct → reverify → resume
- Never release results run since the last acceptable QC
- Document the failure, cause, corrective action, and resume time
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021. (Laboratory quality and management chapters, verify current edition.)
CLSI and Professional Guidelines
- Institutional laboratory SOPs, locally adopted quality policies, and manufacturer instructions for use (IFU). Always verify current local practice.
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