An anal Pap smear (anal cytology) collects cells from the anal canal with a soft swab to look for HPV-related precancer. It's not a blanket CDC recommendation. Current US guidance found the evidence insufficient for routine screening, though some specialty groups now suggest periodic testing for high-risk groups like MSM and people with HIV where follow-up anoscopy is available.
of HPV-attributable cancers
| Item | Value |
|---|---|
| Currently infected | ~42 million |
| New infections / yr | ~13 million |
| Clear within 2 years | ~90% |
| Vaccine prevents | >90% — of HPV-attributable cancers |
What an anal Pap smear actually is
The anal Pap borrows its method from the cervical Pap. A clinician inserts a moistened Dacron swab a few centimeters into the anal canal, rotates it against the walls, and withdraws it slowly to sample cells from the transformation zone, the junction where two cell types meet and where high-risk HPV tends to drive precancerous change. Those cells go into a liquid vial and to a lab, where a cytopathologist reads them for abnormalities.
The biology behind the test is the same one driving cervical cancer. HPV is the most common STI CDC, HPV, and high-risk types — chiefly 16 and 18 — can persist in the lining of the anus and slowly transform healthy cells into high-grade lesions, which can become cancer over years. HPV causes over 90% of anal cancers NCI, so screening the anal canal mirrors what the cervical Pap does for the cervix. For the wider picture of HPV's reach, see our piece on seven viruses causing cancer, including hpv & epstein-barr virus.
How the sample is taken
No bowel prep is needed, and the swab itself is quick, usually under a minute. You'll be asked to avoid douching, enemas, anal sex, or anything inserted in the anus for about a day beforehand so the lab gets a clean cell sample rather than washed-out or disrupted tissue. The swab can feel like brief pressure, but it's not a biopsy and shouldn't be painful.
When to test after exposure
There's no neat window here. The CDC doesn't set a fixed timeframe for HPV: warts and cellular changes can develop months or years after the virus is acquired, and the moment of acquisition can't be pinned down. So an anal Pap isn't an after-an-exposure test the way a chlamydia swab is. It's a surveillance test for slow-moving precancer rather than a read on a recent encounter. For how timing works across other infections, see when to test after exposure.
Who should get screened
CDC's 2021 STI guidance found the data insufficient to recommend routine anal cytology, even for MSM or people with HIV CDC Pink Book. That position predates the 2022 ANCHOR trial, which showed that treating anal high-grade lesions reduced anal cancer in people with HIV. On the strength of that, some specialty groups (IDSA/HIVMA among them) now suggest periodic anal Pap testing for the highest-risk groups, but only where referral for high-resolution anoscopy (HRA) exists, because an abnormal Pap is useless without somewhere to follow it up.
In practice, the people most often considered are:
- Men who have sex with men, who carry a substantially higher burden of anal HPV and anal cancer.
- People living with HIV, in whom HPV persists longer and progresses faster.
- Anyone with a history of high-grade cervical or vulvar precancer, since the same HPV types can affect the anal canal.
- People who've had anal warts or a prior abnormal anal cytology result, who need ongoing follow-up.
There's no routine HPV test for men in general. HPV testing isn't recommended to screen men, adolescents, or women under 30 USPSTF. For women, HPV is found through cervical screening rather than a general STD panel, and never as part of a standard checkup for men. The anal Pap is the exception carved out for specific high-risk anatomy and groups, not a screen anyone can simply request as part of a routine panel.
Getting tested: what the visit is like and what it costs
An anal Pap is almost always done in a clinic — an HIV/sexual-health clinic, a colorectal or GI practice, or a specialty HPV clinic. There isn't a meaningful at-home anal cytology kit, because a usable sample needs proper technique and the result is only actionable if a high-resolution anoscopy referral is on the other end. The whole appointment is short. The swab is the quick part, and most of your time goes to the conversation about your history and risk.
Cost varies by setting and whether insurance treats it as screening or diagnostic, and because it isn't a universal recommendation, coverage can be inconsistent. Call ahead and ask how it's billed. If you're sorting out where to go for related STI screening, you can get tested through standard panels, and you can compare testing providers before you book. A general panel won't include anal cytology; that's a clinic-ordered test.
A common mistake to avoid
People often blur two different problems. The HPV types that cause warts (the low-risk types) are not the types that cause cancer (the high-risk ones). Treating warts doesn't clear the virus, and finding warts doesn't mean you're at higher cancer risk. An anal Pap hunts for high-risk-driven cell changes, not warts, which a clinician diagnoses by looking rather than by cytology.
Reading your results
Anal cytology uses the same vocabulary as cervical Pap reporting. A normal result (often labeled NILM) means no abnormal cells were seen. Abnormal grades run from ASC-US (atypical squamous cells of undetermined significance — borderline changes that may mean nothing) up through LSIL (low-grade changes, usually a transient HPV effect) and HSIL (high-grade changes, the precancerous lesions worth treating). Cytology is a screen that flags who needs a closer look.
Most HPV clears on its own, in most cases within two years, without causing health problems ACS. A low-grade or borderline result frequently reflects an infection the immune system will handle, which is why screening pairs with anoscopy rather than rushing to treat every abnormal Pap.
If your result is abnormal
An abnormal anal Pap leads to high-resolution anoscopy, a clinic procedure where a magnifying scope and a dye highlight suspicious areas so a clinician can biopsy and, if needed, treat high-grade lesions before they progress. For how warts and HPV-related lesions are actually managed (in-office freezing versus prescription creams applied at home over weeks, and why treatment removes the lesion but not the virus), see our overview. Treating warts doesn't clear HPV CDC Tx, so recurrence is common.
When to see a clinician
Book a visit if you notice anal bleeding, a persistent lump or growth, pain, itching, or a sense of fullness that doesn't resolve. Those warrant evaluation regardless of any screening schedule. If you're MSM, living with HIV, or have a history of HPV-related precancer, ask your clinician directly whether periodic anal cytology fits your situation and whether HRA follow-up is available locally. Prevention does the most: the hpv vaccine for adults protects against future infection with the cancer-driving types.