What Is an Anal Pap Smear?
An anal Pap smear is related to a cervical Pap smear. It looks for the cellular changes that are an early sign of anal cancer. Anal cancer, like cervical cancer and throat cancer, is associated with infection with the cancer causing varieties of the human papillomavirus (HPV).
Who Is At Risk For Anal Cancer?
Anal cancer was once thought to be a relatively rare disease that primarily affected elderly women. However, in recent years, the number of cases among men has sharply increased. In particular, rates of anal cancer among MSM are approaching the rates of cervical cancer seen in women prior to the inception of regular cervical Pap testing. In HIV positive men who have sex with men, the rates are twice as high as for HIV negative men. HIV positive women are also at substantially increased risk for anal cancer when compared to women in the general population. In general, receptive anal sex puts an individual at the highest risk of infection with HPV and anal cancer. Anal cancer is one of the most serious potential consequences of HPV in men.
Is the Anal Pap Effective?
The anal Pap smear is comparable in effectiveness to the standard Pap smear. It is relatively good at detecting the presence of abnormal cells, but not terribly good at distinguishing pre-cancerous changes from those changes that are unlikely to cause a problem in the future. It is therefore essential that anal Pap tests only be performed by doctors who have the ability to continue the process of diagnosis with follow up testing and treatment. Follow-up testing may include anoscopy, a non-invasive test similar to a colposcopy, and/or biopsy.
Who Should Get an Anal Pap?
This is the million dollar question. At the moment there are no standardized screening guidelines for anal cancers. This is primarily due to a lack of research, both on screening and on treatment. Some clinicians recommend yearly anal Pap smears for MSM and, in particular, HIV positive MSM. Others suggest testing once every three years, and the CDC currently offers no recommendation at all. If you are at high risk of anal cancer, talk to your doctor about the costs and benefits of screening. He or she should hopefully be able to help you make an informed decision. While research remains lacking, there is no one clear choice. That having been said, the New York State Department of Health AIDS Institute guidelines represent the direction in which most progressive healthcare providers are moving, and so are included below. Bringing a copy of these guidelines with you to your next visit with your healthcare provider may be helpful when discussing anal Pap testing with your doctor.
Clinicians should perform anal Pap tests at baseline and annually in the following populations:
- Men who have sex with men
- Any patient with a history of anogenital condylomas
- Women with abnormal cervical/vulvar histology
Arian et al. (2005) "The Anal Pap Smear: Cytomorphology of squamous intraepithelial lesions." Cytojournal 2:4.
Chiao et al (2006) "Screening HIV-Infected Individuals for Anal Cancer Precursor Lesions: A Systematic Review." Clinical Infectious Diseases 43:223â€“33
Leiman G. (2005) "Anal screening cytology." Cytojournal 2: 5.
Pitts et al (2007) "What Do Gay Men Know About Human Papillomavirus? Australian Gay Men's Knowledge and Experience of Anal Cancer Screening and Human Papillomavirus" Sexually Transmitted Diseases 34(3):170-173.
CDC Fact Sheet HPV and Men. Accessed 12/5/07.
Anal Cancer : To Screen or Not To Screen. Journal Watch 2004. Accessed 12/5/07 at http://aids-clinical-care.jwatch.org/cgi/content/full/2004/0701/1