Quality Control (Lab and Lot Release)
What this domain tests
Quality-control questions test sampling, specifications, testing, out-of-specification handling, calibration and batch/lot release.
Core rules and concepts
- Testing is against an approved specification and validated methods. Results are compared with acceptance criteria.
- Samples must be representative, properly labelled and traceable through chain of custody.
- Instruments need calibration and maintenance; reference standards must be qualified and stored correctly.
- An out-of-specification (OOS) result triggers a documented investigation before retesting; retesting cannot be used to “test into compliance”.
- Lot release applies where batch-by-batch official release is required, often for biological products. A certificate of analysis supports but does not replace release by the competent authority.
Worked example
An assay result is 89.0% against a 95.0–105.0% specification. Reasoning: this is OOS. The analyst should not simply repeat the test until a passing result appears. The laboratory investigates sample preparation, instrument calibration, standards and method suitability, documents the root cause, and only then decides on retesting or rejection. The batch is not released while the investigation is open.
Traps that cost marks
Retesting without an OOS investigation. Using expired reference standards. Releasing a batch on a manufacturer’s certificate alone when official lot release is required. Ignoring chain of custody. Treating calibration as optional.