Laboratory & Diagnostics Engineering
QC controls, Levey-Jennings charts and Westgard rules explained, reagent-lot verification, and centrifuge rotor life limits.
Lab analyzers are unusual among device categories in that a device can be mechanically and electrically perfect and still report clinically wrong results if its chemistry is off - which is why quality control (QC), not just equipment PM, is the primary safeguard for this equipment class, and it's a discipline every technician working in a lab environment needs to genuinely understand, not just defer to the lab staff running it.
Levey-Jennings charts and Westgard rules
Most labs run QC using Levey-Jennings charts - a plot of QC sample results over time against the expected mean and standard deviation - combined with Westgard rules, a set of statistical decision rules for when a QC result pattern means a run should be rejected, even if any single point is technically within the acceptable range. A single point outside 2 standard deviations might just be noise; the same point combined with a second consecutive point outside 2SD, or a run of several consecutive points trending in one direction, is a real signal the rules are specifically designed to catch. A repaired analyzer always gets QC-verified against these rules before its results are trusted again, not just self-test-passed.
Reagent-lot verification
A reagent lot change can produce a result shift that looks exactly like an instrument fault - rule that out first before opening the analyzer. Good lab practice includes parallel-testing a new reagent lot against the old one before fully switching over, precisely so a lot-driven shift is caught and characterized before it gets misattributed to the instrument.
Centrifuge rotor life
Centrifuges have a hard rotor retirement age or cycle-count limit specified by the manufacturer regardless of visible condition, since rotor fatigue from repeated high-speed stress isn't visually detectable, and a rotor failure at speed is a serious, genuinely dangerous mechanical hazard. Track rotor cycle counts as part of routine asset management (Chapter 17), not as an afterthought discovered only when a rotor is already overdue.
Biohazard and exposure considerations
Lab equipment services patient specimens directly, which means bench work here carries real biohazard exposure risk beyond the general infection-control principles in Chapter 15 - appropriate PPE and a documented specimen-handling/decontamination step before opening any analyzer that's had a spill or specimen exposure is standard practice, not an optional precaution.