The detection of abnormalities in cervical cells during a routine Pap test is more common than you might think. Many US women experience equivocal (abnormal cells that may or may not be cancerous) Pap tests every year. Fortunately, in many of these cases, the abnormality disappears without ever causing problems. Unfortunately, in some cases, these abnormal cells go on to become cervical cancer .

Currently, the single most definitive way to determine whether the abnormal cells detected in a woman’s Pap test are actually precancerous or cancerous is to undergo a biopsy procedure called a colposcopy. However, because this procedure is invasive, expensive, and stressful for the patient, it is not a useful screening method for cervical cancer.

Over the years, we have also learned that almost all cases of cervical cancer are caused by infection with one of a number of different types of human papillomavirus (HPV) . Therefore, some clinicians, instead of making a woman wait six to 12 months for a second Pap test, use the HPV test as a way of better ascertaining if a woman’s abnormal Pap test is likely an indication of precancerous or cancerous cells. But is the HPV test as effective a screening tool as the Pap test?

Recently, a group of researchers set out to answer this question. Their study, published in the February issue of the Journal of the National Cancer Institute , found that the HPV screening test is a more sensitive and specific screening test for cervical cancer than a second Pap test.

About the Study

The researchers gathered data from 15 studies on the management of one of the most common abnormalities called atypical squamous cells of undetermined significance (ASCUS) conducted between 1992 and 2002. In all of the studies, the women were given either a repeat Pap smear or an HPV test followed by a colposcopy. This kind of statistical summary of data from multiple studies is called a systematic review, or meta-analysis.

The Findings

The researchers found that the sensitivity and specificity of the HPV test was higher than the repeat Pap smear (84.4% versus 72.9%, respectively. In clinical trials, sensitivity refers to the proportion of the time that a test yields a true positive result. The closer the sensitivity is to 100%, the more likely a positive result will occur when the patient truly has the disease being tested for. Specificity refers to the proportion of the time that a test yields a true negative result. The closer the specificity is to 100%, the more likely a negative result will occur when the patient is truly disease-free. When a test is both sensitive and specific, a positive test indicates that the disease is present and a negative test offers reassurance of good health.

When the researchers looked only at the studies that used a particular type of HPV test, called the Hybrid Capture II assay, they found that HPV testing had a sensitivity of 94.8% and a specificity of 67.3% In comparison, the sensitivity of a repeat Pap smear was only 81.8% and its specificity was only 57.6%.

How Does This Affect You?

The researchers concluded that the HPV test, particularly the Hybrid Capture II screening test was more accurate (higher sensitivity and similar specificity) than the repeat Pap test. Additionally, it is less invasive, less expensive, and less stressful for the patient than colposcopy.

An editorial accompanying the study points out that this meta-analysis, like all meta-analyses has several weaknesses, one of which is that cervical cancer screening is a rapidly evolving field, therefore the quality of tests used over a 10 year period of time may not lend themselves to accurate comparison. However, even in light of this and other limitations, the editorial concludes by saying that the question regarding the efficacy of HPV testing following a mildly abnormal Pap smear is answered (it works!), and that the focus of future research should be on evaluating the need for combination Pap and HPV screening in the general public.

If you have had an abnormal Pap smear, be sure to ask your provider whether HPV testing with the Hybrid Capture test might be indicated. The test is painless, carries no physical risks, and costs little more than the Pap smear. When performed as recommended in this study, HPV testing can offer information the may prove helpful in preserving and enhancing your reproductive health.