Cervical Cytology and HPV Testing
What's New and What You Need to Know
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Published: March 2010Print Record of Viewing
Dr. Michael Henry reviews the current guidelines for the appropriate use of human papillomavirus (HPV) tests.
Presenter: Michael R. Henry, MD
- Director of the Cytology Laboratory in the Division of Anatomic Pathology at Mayo Clinic
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Welcome to Mayo Medical Laboratories' Hot Topics. These presentations provide short discussion of current topics and may be helpful to you in your practice. Our presenter for this program is Dr. Michael Henry, Director of the Cytology Laboratory in the Division of Anatomic Pathology at Mayo Clinic. Dr. Henry will review the current guidelines for the appropriate use of human papillomavirus (HPV) tests.
We are going to be going through a very quick presentation today talking about HPV testing and cervical cytology, covering some new things and some things that I think everybody needs to know about this type of testing.
Anogenital HPV Types
The HPV types that are associated with cervical cancer are called high-risk viral types. There are numerous high-risk viral types but the most common are 16, 18, and what I like to call the odd thirties - 31, 33, 35 and 39. There are a couple of high-risk viral types that are also possible and then a number of HPV viral types that are low-risk and have no significant risk of developing cervical neoplasia.
Mechanism for Transformation
The mechanism for transformation from an infection with an HPV viral type to cervical cancer requires integration of the viral genome into the host genome. Two HPV genes are always conserved when the virus is integrated into the host genome - these are E6 and E7. At the same time, interestingly enough, there is a loss of E2 which normally regulates the transcription of both E6 and E7. Thus, you get an increase in the products from these 2 genes. E6 gene in the human genome inhibits p53.
This allows the cell to enter S phase without the normal DNA repair function. E7 binds the retinoblastoma tumor suppressor gene product (pRb) and again allows cells to proceed uninhibited through the S phase. This combination allows these cells to multiply without the normal regulation. And, interestingly enough, as you notice here, the E6 and E7 gene are viral genes and it's not a mutation of the host genome but actually integration of a different gene into the host genome which allows this transformation.
Natural History of HPV Infections
The natural history of HPV infections is also important to recognize. With the initial infection, the virus will replicate within the cervix or other mucosal tissues, but does not normally integrate itself into the host genome and thus does not always result in a preneoplastic or neoplastic condition. This HPV infected cervix in the majority of women will clear and become completely normal again. In some individuals, there is progression with integration of the HPV into the host genome and this can lead to a precancerous lesion.
Again, in many of these instances, the precancerous lesion will regress back to an HPV infected cervix and this infection may last for quite some time, sometimes even over the entire lifespan of the individual. In very rare instances, the preneoplastic lesions will progress and will progress on to invasive cancer. This is important when we are looking at using HPV testing in cervical cancer screening because again the majority of women who become infected with HPV become completely normal again. They will clear this infection.
HPV DNA Testing in Cervical Specimens: Uses
HPV DNA testing in cervical specimens actually has a number of uses. You can use it as triage for atypical squamous cells of unknown significance or ASC-US in Pap smears and this is one of the most common uses of HPV testing currently being used. You can use it for secondary follow-up of an abnormal Pap smear or a negative colposcopic examination and I am not going to go into this today. You can use it posttreatment in a woman who has been treated for preneoplastic conditions and again I am not going to take about this. You can use it for primary screening and again, the HPV is used along with the cervical cytology and they are both collected at the same time and they are both tested at the same time. And, we will talk about when that should be used in a minute. Then, finally, you can use it as a quality assurance technique and it is very valuable in your laboratory to use this-but again, it is not part of what we are going to be talking about today.
Meta-analysis of ASCUS-HPV Triage Studies
There have been a number of studies which have looked at the use of HPV testing in ASC-US Pap smears for a triage of these patients to colposcopy. A large meta-analysis of these studies has shown that using HPV testing works very well in ASC-US cytology and will separate out the two populations, one of which should go onto colposcopy and one of which can be followed with routine cytology follow-up.
Using a disease threshold of CIN2+ using HPV testing in ASC-US cases yields a sensitivity of approximately 94% with a range of 80%-100% for CIN2 with a reasonable specificity again ranging from 37%-80%. The specificity is lower again because HPV infection does not necessarily correlate with a CIN2 diagnosis.
Studies that have looked at repeat cytology as an indication for colposcopic examination show that using HPV testing yields a significantly higher sensitivity for CIN2+ with essentially equal specificity. These studies show that using HPV testing is a very good method to determine which women need to go on for a colposcopic examination.
2006 Consensus Guidelines-ASC-US
Using these studies, there have been some consensus guidelines which have come out about the use of HPV testing in the background of ASC-US. One of these is the 2006 Consensus Guidelines for the Management of Women with Abnormal Cervical Cancer Screening Tests. This is from the ASCCP which is the American Society of Colposcopy and Cervical Pathology.
These guidelines have been endorsed by a number of professional organizations as listed here. The CETC which is the Cytopathology Education and Technology Consortium has also come out with a statement on HPV test utilization which again has been endorsed by a number of organizations including all of the major pathology organizations. This statement was also published in Archives of Pathology and the American Journal of Clinical Pathology.
The ASCCP Consensus Guidelines for a cytology diagnosis of ASC-US layout several things that can be done with this diagnosis. Repeat cytology, colposcopy or HPV testing are all acceptable methods of following up an ASC-US diagnosis. If repeat cytology is used it should be done at 4-6 months intervals until there are 2 consecutive negative results. Any patient with a repeat ASC-US or higher cytology should be referred to colposcopic examination.
Reflex HPV testing is the preferred test if the initial cytology was collected in a liquid-based preparation or if there was a co-collection for HPV testing. This harkens back to the prior slide which shows the results of HPV testing as being more sensitive than a repeat cytology. All positive HPV patients with a diagnosis of ASC-US should be referred to colposcopic examination.
If the colposcopic examination is negative then there should be repeat cytology at 6 and 12 months or a repeat HPV test at 12 months. HPV should not be done prior to 12 months. A negative HPV with a cytology diagnosis of ASC-US should allow the patient to go back into routine screening, in other words, cytology at 12 months.
2006 ASCCP Guidelines and CETC Recommendations
The 2006 ASCCP Guidelines and the CETC recommendations do have a couple of things to say about special populations, especially adolescents. High-risk HPV testing is not appropriate for the initial triage or management of adolescents, these are women who are under 21 years of age, with any abnormal cytology result. This is because soon after sexual activity, many patients become infected with HPV but the vast majority of these women will clear their HPV infection.
Thus, HPV testing in this adolescent population does not identify a population at significant risk for going on to develop significant preneoplastic dysplasia. Furthermore, if you do HPV testing, the clinician should not be utilizing that information in the follow-up of this individual.
2006 Consensus Guidelines for ASC-US: Special Circumstances
The guidelines also talk about other special circumstances. These include women who are postmenopausal, immunosuppressed, or pregnant. For the diagnosis of ASC-US, none of these women are considered to be a special population and they should be treated the same as the general population. The exception to this is HPV-positive pregnant women who are older than 20 and in these women, colposcopic examination can be deferred until after they deliver their baby. Again, adolescents should not be tested for HPV.
High-Risk HPV Testing
So, when should you use high-risk HPV testing as part of the initial testing in GYN cytology? It is appropriate only in specific populations. In postmenopausal women you can use it as part of the routine screening in conjunction with regular cytology. This is an FDA approved test.
Patients with an initial cytologic diagnosis of ASC-US, HPV can be used as part of the triage. Patients with a cytologic diagnosis of low-grade squamous intraepithelial lesion (LSIL) who are postmenopausal can also be tested for HPV prior to colposcopic examination if the HPV is negative, then they are not at significant risk for developing a significant lesion and may be followed.
For women who are greater than 30 years of age, HPV again can be used as part of the routine screening in conjunction with cytology and if both cytology and HPV are negative, then these individuals should not be screened again for 3 years. Patients with a cytologic diagnosis of ASC-US, again HPV can be used as a triage mechanism to determine which ones need to go on to colposcopic examination. For women between the ages of 20 and 30, HPV should only be used as triage for ASC-US.
Low-Risk HPV Testing
And finally, low-risk HPV testing. There is no role for the use of low-risk HPV testing for cervical disease. Both the ASCCP and the CETC in their recommendations state that testing for low-risk HPV has no role in routine cervical cancer screening or for the evaluation of women with abnormal cervical cytology.