Quality Assurance and Troubleshooting
QA vs QC
Quality assurance is the overall system that ensures reliable results; quality control is the specific checks within it (controls, monitoring, records). Candidates should understand that QA includes pre-analytical, analytical, and post-analytical phases, and that documentation is central-if it is not recorded, it did not happen.
Troubleshooting logic
Troubleshooting is cause-and-effect reasoning. Start with the artifact and work backward: is it in the tissue (fixation, processing), the block (embedding, infiltration), the section (microtomy, floatation), or the stain (reagents, timing)? A systematic approach beats guessing. For example, a uniformly pale H&E could be under-staining, exhausted hematoxylin, or over-differentiation; each has a different corrective action.
Controls and monitoring
Controls validate each run. Positive controls confirm the stain works; negative controls detect nonspecific binding. Equipment monitoring (temperature logs, processor checks) and reagent logs are part of QC.
Traps
Common traps: blaming the stain for a processing problem, or assuming a single bad slide means a systemic failure. Another trap is confusing a corrective action with a preventive action. Questions may ask what to do first-usually verify the control and the reagent, not re-cut the block.
Worked example
If only one slide in a batch is poorly stained while controls are fine, the problem is likely local (that slide or section), not the reagent. If all slides are pale and the control is also pale, suspect the reagent or protocol.