How is it used?
Traditionally, genital HPV infection has been detected as abnormal cell changes on a
Pap smear, a test used primarily to detect
cancer of the cervix (the lower part of the uterus or womb) or conditions that may lead to cancer. During a Pap smear, the "normalness" of cervical cells is evaluated under a microscope. "Low-grade" changes to the cells on a Pap smear may indicate an HPV infection, but there is no clear distinction between high- and low-risk types.
testing for HPV has gained widespread acceptance as an additional cervical cancer screening tool and as follow-up to abnormal changes detected with a Pap smear. There are now several such DNA HPV tests, some of which have been approved for marketing by the FDA, that can detect either the majority of the high-risk types of HPV or specific subtypes, such as HPV-16 and HPV-18.
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When is it ordered?
The American Cancer Society recommends that women over the age of 18 and all sexually active women have a
Pap smear yearly to screen for cancer or situations that may develop into cancer. In women over 21, when results indicate abnormal changes that may be due to a high-risk type of HPV, then DNA HPV testing may be ordered as a follow-up test.
The American College of Obstetricians and Gynecologists (ACOG) released guidelines in August 2003 recommending that women 30 years or older be offered an HPV DNA test in addition to their Pap smear and pelvic exam. If the HPV DNA test and Pap smear are negative and the woman does not have an underlying health condition, such as HIV or , then the guidelines suggest that she may wait three years before having another Pap smear and HPV DNA test. Patients who are positive for high-risk HPV, have abnormal cell changes on their Pap smear, or have underlying medical conditions should be screened more frequently, with the frequency to be determined by the patient and her doctor on an individual basis.
The HPV DNA test is not recommended for screening women younger than age 30 because infections with HPV are relatively common in this age group and often resolve without treatment or complications. However, it may be used as a follow-up test in women who are 21 years or older and who have certain abnormal results on a Pap smear known as "atypical squamous cells of undetermined significance" (ASC-US) [see Pap smear Terminology] to determine the need for colposcopy, a procedure that allows a doctor to visually inspect the vagina and cervix under magnification for the presence of abnormal cells.
See Screening: Cervical Cancer (ages 19-29), (ages 30-49), (ages 50 and up)
Some doctors will test men who fall into a high-risk category. Men who have sex with men and those who have HIV may be tested for HPV. Evaluating the risk of HPV-related diseases of the anal canal in men is becoming more common.
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What does the test result mean?
On a
Pap smear, ASCUS and "low-grade" changes indicate the likely presence of HPV and the need for further testing. A positive HPV DNA test indicates the presence of a high-risk type of HPV, but the test does not specify which type is present. If the HPV DNA test is negative, it is unlikely that there is a high-risk HPV infection. If the Pap smear is abnormal but the HPV DNA test is negative, then follow-up testing and further monitoring are indicated. Likewise, if the Pap smear is normal but the HPV DNA test is positive, additional testing may be necessary.
The tests most commonly used to screen for HPV only detects those types that have a higher risk of progressing to cancer. If positive, it indicates the presence of one of these high-risk types:
- HPV types 16, 18, 31, 33, 39, 45, 51, 52, 56, 58, 59, 66, 68, and 73
Sometimes, molecular tests to detect and identify low-risk HPV types are ordered. If the result is positive, it indicates the presence of one of the low-risk types:
- HPV types 6 and 11 that typically cause venereal warts, along with types 42, 43, and 44 have a low risk of progressing to cancer.
A test approved by the FDA in 2009 identifies the specific HPV subtypes 16 and 18. If this test is positive, it indicates the presence the subtypes that cause 70% of cervical cancer.
A doctor might take a small piece of tissue (a ) from the cervix and examine it under a microscope. When either the Pap smear or the biopsy indicates a condition that could lead to cancer in some women (called intraepithelial neoplasia), a DNA HPV test can determine if the patient is infected with a high-risk strain of HPV that increases the chance that cancer might develop if not treated.
Recently, some doctors have screened men who are at a high risk for sexually transmitted diseases for HPV-related anal cancer. The test is similar to a cervical Pap smear where the anal lining is swabbed and the cells are examined under a microscope. HPV DNA tests can also be performed on these samples. As in cervical samples, positive results will need to be followed up by your doctor with further testing, including a more thorough exam and possible biopsy.
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Is there anything else I should know?
Although very rare, a pregnant woman may pass HPV to her baby during vaginal delivery, resulting in warts in the throat or voice box (laryngeal papillomatosis or recurrent respiratory papillomatosis, RRP).
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