Quality Control & Assurance Flashcards

Which Levey-Jennings rule states that a run is out of control when two consecutive control values exceed the same 2s limit on the same side of the mean?

Answer: 2₂s rule

The 2₂s Westgard rule flags a run when two consecutive controls both exceed +2s or both exceed -2s, indicating systematic error.

A histology laboratory notices that hematoxylin staining is progressively weaker over 48 hours despite no reagent changes. What is the most likely cause?

Answer: Oxidation of hematoxylin solution

Hematoxylin solutions oxidize over time, reducing their staining capacity, which is why ripened or oxidized solutions must be monitored and replaced.

What is the primary purpose of running a negative control in immunohistochemistry?

Answer: Demonstrate that non-specific background staining is absent

A negative control (using a non-immune serum or omitting the primary antibody) confirms that any staining seen in test sections is specific, not background artifact.

Which document records the step-by-step procedure for performing a specific staining technique and serves as the foundation for laboratory quality assurance?

Answer: Standard operating procedure (SOP)

A Standard Operating Procedure (SOP) provides written, validated instructions ensuring each test is performed consistently and reproducibly.

A frozen section stained with Oil Red O shows no lipid droplets, but the pathologist expects lipid. Which control failure is most likely?

Answer: Tissue was fixed in formalin before sectioning

Oil Red O stains neutral lipids in fresh or frozen tissue; formalin fixation and paraffin processing dissolve lipids, preventing staining.

According to CAP accreditation requirements, how often must staining controls for routine H&E be run?

Answer: With each staining run

CAP requires that a control tissue section be included with each staining run to verify that reagents and procedure are performing correctly.

A microtome blade leaves regularly spaced horizontal lines across every section. What quality issue is this, and what is the corrective action?

Answer: Knife lines; replace or reposition the blade

Regularly spaced parallel lines ('knife lines') are caused by nicks or debris on the blade edge and are corrected by repositioning or replacing the blade.