Pap Smear (cont.)

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What is the current status of human papilloma virus (HPV) testing?

HPV is a sexually transmitted virus that may be spread from one person to another even when the genital sores are not visible. Many sexually active people are carriers of HPV, very often without even knowing they are carriers. It is estimated that up to 60% of sexually active women harbor this virus on their cervix or in their vaginal area. It is not unusual for a woman to be unaware that she has HPV - only to find out that her Pap smear shows evidence of HPV.

HPV is not curable, although the cellular damage it causes is generally treatable and a vaccine against the four most commonly found HPV types is available. A woman with HPV needs careful and regular long-term medical follow-up to watch for any resulting HPV-associated pre-cancerous cellular changes.

There are over 70 different strains of HPV virus. Based on the observation that certain strains of HPV (for example, types 16 and 18) are more likely to be associated with cervical cancer, some people have advocated testing HPV infected women in order to identify their specific strain of HPV. Following an abnormal Pap smear, this information would then be used to help select the specific treatment strategy. In other words, a physician would more aggressively treat a woman with an abnormal Pap smear if she tests positive for an HPV type that is more likely to be associated with the development of cervical cancer.

However, even the so-called "low-risk" HPV strains can still be associated with cervical cancer at some time in the future and not all of the high-risk HPV strain abnormalities will necessarily result in cervical cancer. Furthermore, the HPV typing is expensive. The main use of HPV testing in screening for cervical cancer is for determination of treatment and follow-up recommendations for women with Pap smears interpreted as atypical squamous cells of undetermined significance (ASC-US) . Those with positive tests for high risk HPV types and an ASC-US smear are referred for further evaluation.

HPV testing along with Pap screening (a combined test) was approved for primary screening for cervical cancer by the U.S. Food and Drug Administration (FDA) in 2003. This combined testing has been used as an alternative screening test for low risk women aged 30 and over at intervals of three years or greater.

When should women start and stop having Pap smears, and how often should Pap smears be performed?

The table summarizes the consensus of all the major organizations regarding these important questions. The key points of the table are as follows:

  • All the guidelines agree that Pap smears should be started within 3 years of first sexual activity or age 21, whichever comes first.
  • There are minor differences in the recommendations for the frequency and age at which to stop Pap smears.
  • Older women who have had many normal Pap smears in a row and have been regularly screened are highly unlikely to have an abnormal Pap smear. These findings point to stopping Pap smears in older women, as reflected by several of the guidelines in the Table.
  • Women who have had a total hysterectomy for a benign condition no longer have a cervix, and thus do not derive any benefit from screening for cervical cancer.
  • In contrast, women who have had a subtotal hysterectomy still have a cervix, and thus should be screened according to the recommendations of women who have not had a hysterectomy.
  • Women who have had a hysterectomy for abnormal Pap smears have their own special recommendations.

Special situations may impact the frequency of screening. For example, women who have had cervical cancer, exposure to diethylstilbestrol, or a compromised immune system (as with HIV infection, for example) should continue annual screening as long as they are in reasonably good health. Women who have had a hysterectomy for CIN2 or CIN3 (a type of abnormal Pap smear) should be screened until they have had three normal Pap smears, (and if no abnormal Paps show up in 10 years, they can stop having Pap tests).

Medically Reviewed by a Doctor on 2/21/2014

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