Cytology: liquid-based cytology

11 Kerala PSC Lab Technician Gr II practice questions on Cytology: liquid-based cytology, part of Pathology. The first 11 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   In the ThinPrep method, on what are the cells first collected to form the thin layer?

   1. AA filter membrane
   2. BA paraffin cell block
   3. CA density gradient
   4. DA cytospin funnel

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   Answer: A · A filter membrane

   The ThinPrep processor disperses the sample and draws the fluid through a polycarbonate filter membrane until enough cells have collected on it. The filter is then pressed onto a glass slide, leaving an even layer of cells in a circle about 20 mm across. SurePath instead uses density gradient centrifugation followed by settling. In both methods the slide is fixed at once and Pap stained.

   • B: A cell block is a paraffin-embedded pellet, not a thin-layer slide.
   • C: Density gradient separation is the SurePath method, not ThinPrep.
   • D: A cytospin funnel is used in cytocentrifugation of body fluids.

2. Question 2 · Easy

   For liquid-based cytology, what kind of fluid is the cervical sample collected in?

   1. ABouin's fluid
   2. BNormal saline
   3. C10% neutral buffered formalin
   4. DAlcohol-based preservative fluid

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   Answer: D · Alcohol-based preservative fluid

   LBC vials hold an alcohol-based preservative (methanol-based in ThinPrep, ethanol-based in SurePath). The cells are fixed the moment they enter the vial, so air-drying artefact is avoided. Nearly all the collected cells go into the vial instead of staying on the brush. The vial is then processed in the laboratory to make a thin-layer slide.

   • A: Bouin's fluid is a picric acid tissue fixative, not a cytology collection medium.
   • B: Saline does not fix cells; they would degenerate before processing.
   • C: Formalin is a tissue fixative and is not used in LBC collection vials.

3. Question 3 · Medium

   All of the following are advantages of liquid-based cytology EXCEPT:

   1. AResidual fluid for HPV testing
   2. BA smaller area to screen
   3. CLower cost per test
   4. DFewer unsatisfactory samples

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   Answer: C · Lower cost per test

   LBC costs more than a conventional smear because it needs special vials, a processor and consumables. Its gains are fewer unsatisfactory samples (less blood, mucus and air-drying), a small thin-layer circle that is quicker to screen, and leftover fluid for HPV and other tests. Laboratories weigh these benefits against the extra cost. Staff also need training, because cells look slightly smaller and the background is cleaner than on a conventional smear.

   • A: Testing the leftover fluid for HPV is a true advantage of LBC.
   • B: The small, even circle of cells is quicker to screen; this is an advantage.
   • D: Fewer unsatisfactory samples is a true advantage of LBC.

4. Question 4 · Hard

   A ThinPrep cervical slide has too few squamous cells because the sample was very bloody. Fluid is left in the vial. The best next step is to:

   1. ASpin the vial and smear the whole deposit
   2. BAdd formalin to the vial and reprocess
   3. CWash with glacial acetic acid and reprocess
   4. DRestain the same slide for longer

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   Answer: C · Wash with glacial acetic acid and reprocess

   Heavy blood is a common cause of a scanty ThinPrep slide, because red cells crowd the filter before enough epithelial cells are collected. A dilute glacial acetic acid wash (usually 9 parts CytoLyt to 1 part acid) lyses the red cells, and the washed sample is run again. Formalin cross-links the cells and does not remove blood. Restaining cannot add cells, and a smear of the whole deposit would still be obscured by blood.

   • A: A smear of the whole deposit would still be obscured by red cells.
   • B: Formalin fixes cells and blood alike; it does not lyse red cells.
   • D: Restaining cannot add squamous cells that are not on the slide.

5. Question 5 · Medium

   In ThinPrep processing of non-gynaecological samples such as urine, CytoLyt solution is used mainly to:

   1. ACross-link proteins like formalin
   2. BStain nuclei before transfer
   3. CClear cells before mounting
   4. DLyse red cells and dissolve mucus

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   Answer: D · Lyse red cells and dissolve mucus

   CytoLyt is a buffered, methanol-based wash and transport solution. It lyses red cells, dissolves mucus and prevents protein precipitation while preserving the cells. The washed cell pellet is then put into PreservCyt solution and run on the processor. Bloody or mucoid fluids give far fewer unsatisfactory slides after CytoLyt washing.

   • A: CytoLyt is alcohol-based and does not cross-link proteins like formalin.
   • B: Staining is done after the slide is made, by the Pap method.
   • C: Clearing in xylene comes at the end of Pap staining, just before mounting.

6. Question 6 · Hard

   A clinic's ThinPrep cervical samples are often reported as having too few cells, though collection looks correct. The vials are clear, not bloody, and staff apply lubricant gel to the speculum. The most likely cause is:

   1. ALubricant gel clogging the filter
   2. BHeavy blood in the samples
   3. CMethanol fixative in the vial
   4. DStorage for two days before processing

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7. Question 7 · Medium

   In the SurePath method, the detachable head of the collection brush is dropped into the vial and sent to the laboratory. Why?

   1. ASo the brush can be sterilised and reused
   2. BTo act as a filter during processing
   3. CSo no cells are lost on the device
   4. DTo keep the vial from leaking

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8. Question 8 · Easy

   Liquid-based cytology slides are called monolayer preparations because the cells:

   1. ALie in one thin, non-overlapping layer
   2. BAre all of a single cell type
   3. CAre fixed in a single fixative
   4. DAre stained with a single dye

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9. Question 9 · Medium

   A cytology screener trained on conventional Pap smears starts reading liquid-based slides. Which difference must the screener allow for?

   1. ANuclei stain paler and chromatin cannot be judged
   2. BCells are larger and spread flatter than in smears
   3. CInflammatory cells are absent from every slide
   4. DTumour diathesis clings to cells as small clumps

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10. Question 10 · Easy

    The ThinPrep PreservCyt collection solution is mainly a buffered solution of:

    1. AGlutaraldehyde
    2. BFormaldehyde
    3. CMethanol
    4. DAcetone

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11. Question 11 · Easy

    A liquid-based cervical slide is usually quicker to screen than a conventional smear mainly because:

    1. AOnly abnormal cells reach the glass slide
    2. BIt is stained without any haematoxylin
    3. CIts cells lie in one small, clean circle
    4. DIt is screened at low power only

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