Anal Swab Tests

Anal swab tests

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

How is it collected?


Although there are few published data on this, 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.

This is typically done by a trained clinician, but research is under way to see whether this can be done by the patient themselves, avoiding the need for a potentially embarrassing examination. 

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?

The swab is typically tested for one of two things:

  1. HPV – There are several types of tests available, which use slightly different technologies, all of which are very sensitive. Typically, it will tell you whether you have high risk HPV in your anal canal. This finding is very common, particularly in gay men. It is worthwhile discussing the result with your doctor, who may advise you to have further investigations.
  2. Anal cytology - 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 cytology swabs, 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.