Is HPV detectable in urine?

Human papillomavirus (HPV) is a very common virus that can lead to cancer in some people. There are over 150 types of HPV, with around 40 types that can infect the genital areas. Some types of HPV can cause genital warts while others may lead to cancer. The high-risk types of HPV that can cause cancer include HPV 16 and 18, which together cause about 70% of cervical cancers.

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Can HPV be detected in urine?

HPV typically infects the skin and mucous membranes in the genital areas. It is most commonly detected from cervical cells obtained by a Pap smear or swab of the cervix. HPV can also be detected from the penis, vagina, vulva, and anus. Less commonly, it may be detected in the mouth or throat. However, HPV usually cannot be reliably detected from urine samples.

A few small studies have looked at detecting HPV DNA in urine, with mixed results:

One study found HPV DNA in 10% of urine samples from women infected with HPV. However, HPV type could not be identified.
Another study detected high-risk HPV DNA in 17% of urine samples from women with cervical precancer or cancer. However, detection rate was much lower than from cervical samples.

A study in men found HPV DNA in around 13% of first-catch urine samples among men with genital warts. Detection rate was again much lower than from penile swabs.

Based on current evidence, testing urine samples is not a reliable method to detect an HPV infection. There are a few reasons why HPV DNA is typically not found in the urine:

HPV infects the epithelial cells of the skin and mucous membranes. Shedding of infected cells into the urine is limited.

Urine contains fewer cells compared to cervical, vaginal, or penile swab samples.
Any HPV DNA present may get diluted in the large volume of urine.
Contamination of the urine sample with HPV DNA is possible during collection.

When should HPV testing be done?

The guidelines recommend HPV testing in the following situations:

Cervical cancer screening: HPV testing is recommended along with the Pap smear for women aged 30-65 years old. HPV testing is more sensitive than the Pap smear in detecting cervical precancers.
Follow up of abnormal Pap results: If the Pap smear is abnormal, an HPV test may be done on the cervical sample to determine if the changes are related to an active HPV infection.

After treatment of cervical precancer: An HPV test may be done after 6-12 months to confirm the precancerous lesion has been successfully treated.
HPV testing in men: HPV testing is not recommended for male cancer screening. However, it may be used in follow up of genital warts or high-grade precancers on the penis, anus or oropharynx.

HPV testing is done on a sample of cervical cells obtained by a Pap smear or swab of the cervix. It can also be done on vaginal, vulvar, anal, penile, or oropharyngeal samples. Urine samples are not adequate for reliable HPV detection with current testing methods.

HPV test results

HPV tests look for the presence of high-risk HPV types, most commonly types 16 and 18. There are two main outcomes from an HPV test:

Positive: A positive test means HPV is detected. A positive HPV test after treatment could mean persistent infection or possible recurrence.
Negative: A negative HPV test means high-risk HPV is not detected. This typically means any cervical cell changes are not due to high-risk HPV.

What the results mean depends on the reason for testing:

For screening: Women who are HPV negative have a very low cancer risk and can continue routine screening. If HPV positive, further testing with Pap smear or colposcopy is needed.
After abnormal Pap: An HPV negative result means changes are likely not significant. An HPV positive result means precancer or cancer is more likely.

After treatment: An HPV negative result usually indicates successful treatment. A positive result may prompt further evaluation and possible retreatment.

How accurate are HPV tests?

HPV tests detect current infection by high-risk HPV types. Overall, they are more sensitive but less specific than the Pap smear for detecting cervical precancers. Accuracy depends on the testing situation:

For screening: HPV testing alone detects around 90% of cervical precancers compared to around 75% with Pap smear alone. However, HPV testing can have more false positives.

With abnormal Pap: Adding HPV testing increases accuracy. HPV positive result confirms precancer in over 90% while HPV negative means small precancer risk.
After treatment: HPV testing accurately identifies treatment failure in 60-90% and rules out residual disease in around 95%.

No screening test is 100% accurate. HPV testing is more sensitive for detecting precancer than the Pap smear, but there is still a small chance of false negatives. Multiple normal test results over time provide more reassurance. All abnormal screening results should be followed up appropriately.

Can HPV infection be diagnosed from urine?

There is currently no accurate test to diagnose an active HPV infection from urine samples. Reasons include:

Low levels of HPV present in urine compared to genital samples
Inability to determine HPV types from urine

Risk of false negative results

Instead, HPV infection is diagnosed using tests on samples from potentially infected sites, such as the cervix, vagina, vulva, penis, anus or oropharynx. Swabs and brushings collect infected cells from these surfaces for HPV DNA testing.

A cervical HPV test, along with a Pap smear, remains the preferred way to screen for cervical cancer and precancers. Urine HPV testing is still experimental and not recommended by guidelines.

Risks from a urine HPV test

There are some potential harms from relying on urine samples to test for HPV infection:

False reassurance: A negative urine test could miss an actual HPV infection, delaying further diagnostics and treatment.
Over-diagnosis: Urine likely contains HPV from past cleared infections. A positive urine test could lead to unnecessary procedures if infection has already resolved.

Over-treatment: Treating HPV infections that would have otherwise cleared on their own can cause harm, like cervical incompetence after cone biopsy.
Misunderstanding: Results may be misinterpreted, as urine testing does not confirm cervical or genital HPV infection.

Due to the high risk of inaccurate results, current guidelines advise against HPV screening through urine samples. False negatives are especially concerning, as they may delay cancer detection in infected individuals.

Conclusion

HPV testing on urine samples is still considered experimental. Based on current evidence:

HPV DNA is infrequently detected in urine, even in those with cervical infections.
Urine testing underestimates true HPV infection rates compared to cervical/genital testing.

HPV types cannot be accurately identified from urine samples.
There is a high risk of inaccurate results leading to under or over-diagnosis.

While urine testing remains appealing for its non-invasive nature, current methods lack the accuracy to reliably diagnose active HPV infections. Further research is still needed to improve test performance in urine specimens. For now, HPV testing is only recommended on samples from potentially infected mucosal sites rather than urine or other bodily fluids.

Cervical cancer screening guidelines continue to recommend HPV testing alone or with Pap smear for women aged 30-65 years. However, urine samples are inadequate for HPV screening with today’s technology. Cell samples collected from the cervix remain the most accurate way to detect high-risk HPV infections.

In summary, HPV cannot be reliably detected or diagnosed from urine at this time. Cervical/genital sampling and HPV DNA testing provide the most accurate way to determine if a clinically relevant HPV infection is present.