Cervical Screening Programme
Department of Health
The Government of the Hong Kong Special Administrative Region

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The sensitivity of the cervical smear depends greatly on the quality of the smear.

  • Appropriate timing: avoid cervical screening during menstruation because blood stained smear may be difficult to interpret and may give rise to false negative smear results.

  • Correct site of sampling (transformation zone).

  • Adequate cervical cells obtained (both ectocervical and endocervical components) using appropriate sampler: the presence of endocervical cells on the sample has been recommended as a marker of adequacy of cervical cell collection as they imply the upper limit of transformation zone was included in the specimen.

  • Proper fixation and proper storage of specimen.

  • Correct labeling of specimen and cytology request form filled with adequate clinical details.

  • Timely delivery to laboratory.

Common reasons for screening failure leading to false negative results:

Causes of false negative results
Source of error Solution
Sampling failure
- Failure in sampling the abnormal area
- Failure in obtaining adequate cellular component for diagnosis
- Excessive blood, traumatized cells, mucus or inflammation
- The lesion fails to exfoliate despite adequate sampling.
- Ensure adequate exposure of cervix
- Target the sampler towards the transformation zone
- Circumferential collection of adequate samples
Transfer failure
- Failure in transferring the abnormal cells onto the slide. Only about 20% of cells collected can be transferred to the slide.
- Unsatisfactory preparation of the slide such as blood smear with traumatized cells, layering of cells, air-drying of slide and fixation artefact
- Liquid-based cytology may provide better cells sample
- Fixate soon after taking the smear
Laboratory failure
- Smear of poor quality
- Cells distorted by air-drying
- Scanty material for interpretation
- Liquid-based cytology may provide better cells sample
- Properly trained staff for slide interpretation
- Computer assisted slide interpretation
  1. Timing of Cervical Smear Taking
  2. Communication with Clients
  3. Equipment for Smear Taking
  4. Right Environment & Correct Positioning
  5. Insertion of Speculum
  6. Cervical Cells Sampling
  7. Management of Cells Collected
   
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