HPV DNA Test for Cervical Cancer

by Dr. Hsien-Hsien Lei
Posted October 22, 2007 in DNA Testing

Two recent studies have shown that the human papillomavirus (HPV) DNA test is more accurate than the traditional Pap smear for cervical cancer.

• The HPV DNA test detected 95% of cases in which participants had precancerous changes in the cervix
• The Pap test detected 55% of cases.
• The HPV DNA test had a false positive rate of 6%
• The Pap test had a false positive rate of 3%

When I first saw this news, I breathed a sigh of relief that perhaps sometime soon I would be able to skip regular pelvic exams and cervical cell sampling.

That would be wrong.

According to Lab Tests Online, the HPV DNA test still requires a sample of cells from the cervix. It is NOT a blood test. I emphasize this point because most of the news I’ve seen either got it wrong or didn’t clarify the testing procedure. For most people, DNA tests still mean a blood test even though DNA can be extracted from other samples, such as the ubiquitous cheek swab.

Currently, the HPV DNA test is used in combination with the traditional pap smear. However, recent studies have shown that HPV testing may be used alone and make it possible for women to prolong the time between exams.

One drawback to the HPV DNA test is cost; it is $90 compared to a $10 to $20 Pap test. Also, even girls vaccinated against HPV will need to be screened because there is more than one cancer causing strain not covered by the vaccine.

For more and a video news report, see CBS News.

Photo: HPV infection in squamous cells from Wellcome Images under Creative Commons

Tags: genetics, genes, dna, hpv, cervical cancer, human papillomavirus, pap smear, pap test, hpv dna test

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10 Comments »

Comment by NA

2007-10-22 15:37:29

Let me see if I get this straight. Based on the data given here, the DNA test has a higher false positive rate and costs more then the HPV test?

How many cases did the DNA test catch compared to the HPV tests?

If the DNA test catches more cases then the HPV, then the DNA test might be a better choice for females to have, however, the higher false positive rate is a concern.

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Comment by Hsien-Hsien Lei, PhD

2007-10-22 15:39:59

In this case, better a false positive than a false negative. False positive women will go on to find out that there’s nothing to worry about with further diagnostic testing. False negative women, on the other hand, who have precancerous lesions or cervical cancer will go on without treatment when they absolutely need it.

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Comment by Barry Starr

2007-10-22 19:08:42

Good point Hsien although a false positive can be pretty hard to deal with. My stepmother still remembers her false positive breast cancer result. Am I reading the results correctly that a pap smear gives a false negative 45% of the time and the HPV test a false negative 5% of the time? If so, I know which one I want my wife to have…

(Comments wont nest below this level)

Comment by Hsien-Hsien Lei, PhD

2007-10-22 19:13:29

The good news is that cervical cancer, if caught early, is highly curable.

From the American Cancer Society:

“The 5-year relative survival rate for the earliest stage of invasive cervical cancer is 92%.”

The results I listed above are actually sensitivities and false positives. The sensitivity of the HPV DNA test is 95% while the Pap smear is 55% sensitive.

Sensitivity =
True Positives/(True Positives + False Negatives)

Ahh. Don’t you just love epidemiology!

 

Comment by Barry Starr

2007-10-22 23:14:02

Thanks, I never had epidemiology!

 

Comment by Hsien-Hsien Lei, PhD

2007-10-23 08:50:16

Barry, I often forget I’m actually a trained epidemiologist!

 

Reply here

 

 

 

Comment by NPs Save Lives

2007-10-22 20:27:24

It’s very important that patients get their preventive testing done on a regular basis. Too many times people say “would have, should have, could have” in hindsight.

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Comment by Hsien-Hsien Lei, PhD

2007-10-22 20:30:47

Thanks for the reminder. I’m going in for my smear next Friday. After having skipped it for a number of years. /me hides in shame

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Comment by Mary

2007-10-23 05:53:21

Many of my friends at pozgroup.com are talking about this news. What they care most is if the new DNA test can change the positive result given by pap test. Is it possible to be tested as positive with pap, while negative with this new DNA test? You know, wrong test result of STD can really make a big change in your life.

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Comment by Hsien-Hsien Lei, PhD

2007-10-23 08:54:37

Hi Mary, That’s a very important question. From what I understand (keep in mind, I’m not an STD expert), taking one test won’t affect the results of the other. According to the Canadian study:

“Performance was unaffected by the sequence of the tests. The sensitivity of both tests used together was 100%, and the specificity was 92.5%”

So having both tests will guarantee that every person with cancer will be detected while there will be some false positives that can be clarified with further exams.

Hope this helps!

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