Anal Papanicolau ("Pap") smears

Anal Pap smears are currently being evaluated for a possible role as screening tests for anal pre-cancer. The procedure involves the sampling of cells from the anal canal and uses similar technique to those used in cervical cancer screening.

How is it collected?

Swab and transport medium for anal Pap specimen

It does not seem to matter whether you douche (wash inside the anus) before having an anal Pap.

You will first be asked to take down your lower garments, before lying on your left side. The sample will then be collected by inserting a moistened swab 5cm into the anal canal and firmly rotating it for about 1 minute. The material from this swab is then mixed with solution in the container and sent to the laboratory for analysis.

Are there any side effects?

The procedure may be a little uncomfortable. There may be some minor bleeding immediately afterwards, particularly for those with pre-existing lesions of the anal canal, such as anal warts. It is possible that you will notice a small amount of blood in your first bowel motion following the procedure, but this should not persist.

What do the results mean?

Results typically take two weeks to become available.

The sensitivity of this test is quite low – in other words, it sometimes misses cases of HSIL and cancer. Also, on occasions, the result may be misleading. For these reasons, it is only currently performed in specialist centres, and you must discuss the meaning of your result carefully with your specialist.

The table below lists the common results of anal Pap smears, and gives some possible implications.

Result Other name    Possible implications
Unsatisfactory   Not enough material in the specimen for the laboratory to make a diagnosis. Needs to be repeated.
Normal   No abnormal cells seen.
Atypical squamous cells of uncertain significance (ASCUS) PLSIL  No seriously abnormal cells seen, but some suspicious cells means that further assessment may be indicated. Most commonly found with low risk HPV infection.
Low grade squamous intraepithelial lesion (LSIL) AIN 1  Probable infection with low-risk HPV. Regarded as being at low risk of developing anal cancer.
Atypical squamous cells of uncertain significance – possible high grade (ASC-H) PHSIL Some suspicious cells means that further assessment may be indicated.
High grade squamous intraepithelial lesion (HSIL) AIN 2,
AIN 3
Probable infection with high-risk HPV. Regarded as being at increased risk of developing anal cancer. High resolution anoscopy may be indicated.

Note: None of the above results indicate that cancer is present.