Laboratory Operations, Quality Assurance, and Safety
Quality management
Laboratory operations rest on written SOPs, document control, competency assessment, proficiency testing, and accreditation requirements (CLIA, CAP). Quality assurance is the overall program; quality control is the day-to-day testing of reagents, equipment, and stains. Monitor temperature logs, equipment maintenance, water quality, reagent lot verification, and new antibody or stain validation. When a quality indicator shifts-pale hematoxylin, weak IHC, poor ribbons-investigate, document corrective action, and verify effectiveness before returning to service.
Safety
Formalin is a carcinogen; OSHA sets a permissible exposure limit of 0.75 ppm as an 8-hour time-weighted average and a 2 ppm short-term exposure limit. Use fume hoods, gloves, goggles, and spill kits; consult SDS and the chemical hygiene plan. Xylene is flammable and inhalation-toxic. Segregate waste, label containers, and never pour chemicals down the drain. Sharps, fire safety, ergonomics, and electrical safety are also fair game.
Traps and a worked example
Questions may swap QA and QC, confuse the PEL with the STEL, or ignore lot-to-lot staining shifts. A single acceptable control does not excuse a trend of fading stains.
Worked example: A new hematoxylin lot produces pale nuclei. Review the positive control, confirm lot verification records, and compare with the previous lot. If the new lot fails, quarantine it, document the corrective action, and revalidate before use-do not simply lengthen staining time without investigation.