Laboratory Operations and Quality Management
Core concepts
Think in three phases: preanalytic, analytic, and postanalytic. Preanalytic errors dominate real-world failures, covering patient identification, collection, transport, and labeling. Analytic quality relies on calibrated instruments, appropriate control materials, and statistically evaluated results. Postanalytic concerns include report accuracy, delta checks, critical value notification, and turnaround time.
Statistical quality control is heavily tested. Plot controls on Levey-Jennings charts and apply Westgard rules: 1-2s is a warning only; 1-3s, 2-2s, R-4s, 4-1s, and 10x indicate rejection. Distinguish random error (imprecision, shifts in scatter) from systematic error (bias, shifts and trends). Know the regulatory framework: CLIA complexity categories, waived testing, proficiency testing, documented competency assessment, and corrective action with root cause analysis. Traceability runs through written SOPs, document control, and change management. Safety topics include bloodborne pathogen precautions, chemical hygiene, spill response, fire safety, and biosafety levels.
Traps
- Rejecting a run on a single 1-2s event; that rule is only a warning.
- Confusing a shift, several points on one side of the mean, with a trend, a progressive drift.
- Filing a proficiency testing result without investigation when it fails.
- Treating an unlabeled or mislabeled specimen as acceptable because the result is urgently needed.
- Mixing accuracy (closeness to truth) with precision (reproducibility).
Rule of thumb
Two consecutive control values more than 2 SD on the same side of the mean define a shift and indicate systematic error, so investigate calibration, reagent lot, and instrument maintenance before releasing patient results.