HT Quality Control & Assurance 2

Question 1

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?

Accepted Answer

2₂s rule

Answer

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

Question 2

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

Accepted Answer

Oxidation of hematoxylin solution

Answer

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

Question 3

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

Accepted Answer

Demonstrate that non-specific background staining is absent

Answer

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.

Question 4

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

Accepted Answer

Standard operating procedure (SOP)

Answer

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

Question 5

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

Accepted Answer

Tissue was fixed in formalin before sectioning

Answer

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

(HT) Histotechnician Certification Practice Test

(HT) Histotechnician Certification Practice Test

HT Quality Control & Assurance 2