Vol. 10 •Issue 10 • Page 26
CE Offering
Human Papillomavirus and Cervical Cancer Screening
Recent Advances Improve The Clinical Picture
Recent advances in cervical cancer screening include new cytologic collection techniques, revised reporting terminology and triage strategies that involve molecular testing. These improvements offer health care providers the most effective tools to date in the complex labyrinth of cervical cytology management.
The introduction of Pap screening in the 1950s allowed for the detection and treatment of pre-invasive disease and has decreased invasive cancer in the United States by 75%. In parts of the world where women remain unscreened, cervical cancer is second only to breast cancer in incidence and mortality. Cervical cancer is the major cause of death in women of reproductive age in those regions.1 Cervical cancer morbidity and mortality drop dramatically when women are screened.
Providers who perform cervical cancer screening and triage must be able to responsibly communicate the results to women. HPV DNA testing for oncogenic (high-risk) HPV types is now a recommended strategy for identifying women at higher risk for cervical intraepithelial neoplasia (CIN) after a borderline abnormal Pap (atypical squamous cells-unspecified, or ASC-US).2 The decision to triage women directly to colposcopy, accelerated repeat Pap or HPV DNA testing is associated with emotional, economic and safety issues. An understanding of the natural history of human papillomavirus and its role in the initiation of CIN and cancer is imperative.
As testing for HPV status becomes more widely used for both ASC-US Pap triage and primary screening of women older than 30, more NPs will be charged with making evidence-based decisions and providing accurate information to patients about the meaning of HPV DNA status. The role of HPV in the development of abnormal cells and cervical cancer should be discussed with all women at the outset of cervical screening. NPs who use and report this information must understand the significance of a positive HPV DNA test for oncogenic HPV, offering both caution and reassurance as appropriate. In particular, NPs must understand that infection by high-risk HPV is extremely common in young women and is usually cleared to undetectable levels by an immune response. Persistence of high-risk HPV is necessary for the development of significant pre-invasive and invasive disease.
HPV Types and Oncogenicity
Cervical cancer is generally considered a preventable disease due to its long pre-invasive stage. Experts now know that it is caused by the persistence of oncogenic human papillomavirus.3,4 Significant cellular changes with the potential for progression to cancer can be identified on the cervix and treated as a prevention strategy. More than 100 types of HPV have been identified, and approximately 25 play a role in infection of the anogenital tract. These types can be classified into three relative risk categories: low, intermediate and high. The low-risk viruses include HPV types 6, 11, 42, 43 and 44, which are rarely found in association with high-grade squamous intraepithelial lesions (SIL) or cancer. HPV 6 and 11 are the most common initiators of condylomata (genital warts). The intermediate risk types, including 31, 33, 35, 39, 51 and 52, can be associated with invasive cervical cancer, although this association occurs less frequently than with the high-risk types. The high-risk HPV types include 16, 18, 45 and 58. High-risk HPV types are found in women with high-grade lesions (high-grade SIL). They are also common on the cervices of women who will never develop SIL. HPV 16 is the most common cause of squamous cancer. HPV 18 is the most prevalent viral type in adenocarcinomas. Current testing methods for HPV generally combine intermediate and high-risk types into one group (Table 1).5 Currently, no management strategies are available for treating latent HPV infections. A woman who is high-risk HPV-positive on HPV DNA testing but does not have abnormal cells requires careful follow-up. She may develop a lesion or clear the virus over time.
Most high-risk HPV exposure does not lead to intraepithelial neoplasia or cancer. Long-term persistence of the virus is necessary for HPV-induced cancer to develop. Therefore, women at risk for significant disease and neoplastic progression are the minority (10% to 20%) who do not have an adequate immune response to HPV exposure.5 They do not clear high-risk HPV from their genital skin cells.6
High-risk HPV can interfere with the normal protective mechanisms of anti-oncogenes for control over normal cell growth. The ability to inspect cell reproduction for mistakes or mutations in replication can be lost. High-risk HPV causes a loss of apoptosis, the destruction of cells that occurs with a deviation in genetic structure. HPV E6 and E7 genes block the function of anti-oncogenes and cell growth arrest, and cell death does not occur.3,6
The progression of normal cells to severely neoplastic cells is a multi-step process. Integration of HPV into the host cellular DNA appears to be a final step in transformation of the host cell to an immortalized cancer cell capable of invasion. Viral integration appears to occur when loss of host-cellular control and persistence of high-risk HPV result from poorly understood viral, host and cofactor interactions.6 It is important to understand that HPV infection is extremely common, but that most infection is cleared. The development of cancer is rare and requires the confluence of many factors. Some cofactors in the progression of CIN are well-defined (Table 2).
Prevalence and Presentation
HPV is the most common sexually transmitted infection in the female genital tract. Infection with or detection of HPV DNA does not necessarily mean that disease expression will occur.7 Most infections are asymptomatic and most infected women are unaware they are infected. Approximately one-third of sexually active women harbor some form of clinically manifested HPV infection.8 One investigation of sexually active college women found a cumulative prevalence of anogenital HPV infection of 69%.5,9
HPV exposure occurs primarily through sexual intercourse. To become infected, the virus must gain access to basal cells of a squamous epithelial surface, either through minor traumas such as skin abrasion or during sexual intercourse.10 Inoculation of the epithelium of the entire lower genital tract occurs with infection.11
It is important to understand that a condyloma (genital wart) arises from a field of HPV infection. After treatment and resolution of one condyloma, a new occurrence does not represent new infection or re-infection, but active growth from a field of latent HPV infection. A patient’s immune response determines her outcome after exposure. Immune dominance means no visible change or minimal disease expression and easy clearance. Women who develop extensive warts after exposure to HPV 6 or 11, or are refractory with new warts developing more than 9 months after initial appearance, have not demonstrated an adequate immune response.
When external HPV is present, infection of the vagina and cervix is presumed. There is a risk of associated cervical abnormality initiated by the same HPV type that caused the external disease or by a different type. Multiple HPV types can co-exist in genital skin cells. A woman with low-risk HPV 6 or 11 and external condylomata could develop a significant high-grade cervical lesion. She may have been exposed to multiple HPV types.
There is individual variation in response by local and systemic immune mechanisms that influence the course of clinical manifestations. In addition, viral type and individual cofactors determine outcome after exposure. Outcomes range from absence of disease expression to minimally expressed disease to the actively expressed changes of exophytic condylomas, dysplasias and cancers. The most common recognized visible clinical lesion is the condylomata accuminata or genital wart (Figures 1 and 2). The lesions are typically multiple, well-circumscribed, papillomatous growths that may involve the vaginal introitus, the vulva, the perineum, the anus and less commonly, the cervix.10 It is important to be able to recognize the difference between active condylomatous disease and the normal variants of micropapilliferous and microfillamentous change, which are of no clinical significance (Figure 3).
Most HPV infection is not visible to the naked eye and would be considered subclinical. An acetowhite reaction that occurs with application of vinegar to the vulva is presumptive–not definite–evidence of HPV infection. When this skin is biopsied, a histologic diagnosis of HPV change called koilocytosis is possible. This change does not cause symptoms and there is no rationale for treating it (Figure 4).
Cervical cytology is the most common way that changes of HPV infection are diagnosed. Mild effects include atypia and koilocytotic atypia, although koilocytosis is no longer considered pathonomonic for HPV. The more significant cellular abnormalities are graded in their degree of neoplastic progression from low-grade to high-grade. The nomenclature changed in 1988 from the older terms of mild, moderate and severe dysplasia to the current use of CIN 1, 2 or 3. Currently, CIN 1 is in a low-grade category called LSIL (low-grade squamous intraepithelial lesion) and CIN 2 and 3 are combined in the high-grade category as HSIL (high-grade squamous intraepithelial lesion).
The Transformation Zone
The area at greatest risk for malignant transformation in the lower genital tract is the immature epithelium of the transformation zone of the cervix. Understanding squamous metaplasia is the key to understanding HPV-induced intraepithelial neoplasia. In women and men, the external epithelium of the lower genital tract is covered by mature squamous epithelium. The vulva, vagina and the majority of the cervix portio are covered by stratified mature squamous epithelium. The cervical canal is lined with pure columnar (glandular) epithelium. Between these two cell types is an area of changing cells called metaplastic epithelium. This area of normal changing cells is called the transformation zone. The mature squamous epithelium may harbor latent HPV infection, but is fairly resistant to neoplastic or malignant cellular changes. The metaplastic epithelium is at risk for developing abnormally after exposure to HPV due to the nature of its normal change process.
Metaplasia is defined as a transformation from one mature cell type to another type.10 It is a normal process that continues through the female lifespan. Due to factors that include the acid pH of the vagina, environmental conditions, mechanical irritation, changes of hormones and chronic or mechanical inflammation, the villous tips of glandular cells are burned and begin fusing.10 This stimulates metaplasia. The process creates a replacement of metaplastic cells by mature squamous epithelium proximally toward the cervical canal. The line where mature squamous cells end and metaplastic cells begin can often be visualized grossly at exam by the juncture of a smooth, contiguous surface meeting a rougher, red area (Figure 5).
The line where squamous and metaplastic cells meet is called the squamocolumnar junction (SCJ). The SCJ moves proximally up the cervical portio beginning in-utero and proceeding through menopause. Metaplasia and consequent proximal movement of the SCJ is accelerated at puberty and with pregnancy. Its original location is called the original squamocolumnar junction (OSCJ) and appears grossly as a faint pink line. Its current position is called the new squamocolumnar junction (NSCJ). The NSCJ is considered the most important place for assessing neoplastic change on the cervix, and seeing it defines the adequacy of colposcopy. After application of acetic acid, it appears whitened and distinct. It is not always possible to identify this point without the aid of acetic acid and magnification with the colposcope (Figures 5, 6 and 7). Screening by Pap testing is intended to identify women who need a colposcopic exam for more detailed cervical study. The presence of endocervical cells or metaplastic cells on a Pap smear indicates that the SCJ has been sampled. The SCJ in older women and women who have received adequate cervical treatment may be higher up in the canal, making it more difficult to obtain endocervical cells (Figure 8). The male genital skin lacks an area of immature metaplastic epithelium, hence men do not have an area at risk like the female cervix at the transformation zone.
Pre-malignant lesions on mature squamous skin are visible to the naked eye as pigmented, white or red areas of defined abnormality (Figure 9). Biopsy of any suspicious lesion is mandatory before beginning treatment. High-grade disease can occur in areas of benign condylomata. A rational approach to the management of the lower genital tract requires an understanding of the greater risk for malignant transformation of metaplastic cells compared to mature squamous cells.
HPV’s Transient Nature
Experts no longer think that HPV is a chronic lifetime virus. HPV infections of the anogenital tract are usually transient and cleared to undetectable levels in short duration.5 In a study of college women, the median duration of HPV infection was 8 months.9 During 24 months of follow-up, 92% of the HPV DNA-positive women became HPV DNA-negative.9 Another study of young and adolescent women found that 70% of the HPV DNA-positive women became HPV-negative within 24 months of follow-up.12 Low-risk HPV infections spontaneously clear more readily than high-risk types.13
Persistence of HPV and Risk
The development of technologies to detect HPV DNA permit study of transient vs. persistent infection. Women whose HPV infections persist appear to face an increased risk for the development of high-grade SIL and invasive cervical cancer.5 In a study of women lacking colposcopic or cytologic evidence of cervical disease, persistent infection with a high-risk HPV (i.e., detection of the same type of HPV on two or more visits over a 12-month period) was the single most important risk factor for the eventual development of a squamous intraepithelial lesion.5,14 In another study, women whose infection was persistently positive for high-risk HPV were 216 times more likely to develop cervical cancer than women without HPV infections.15 Studies continue to show that although many young women are infected with HPV, only a small proportion remain HPV-positive over time. Women whose high-risk HPV infection persists in genital skin cells are at greatest risk for subsequently developing significant cervical disease.5
Pap Smear Classification
The Bethesda System of reporting Pap smear results underwent notable changes this year (Table 3).16 One major change involved a statement of adequacy. The former designation of “satisfactory for evaluation” implied that the cytologic sample could be interpreted and was of proper cellular composition.10 The middle category of “satisfactory but limited by” was also problematic, and it was eliminated. Such Pap smears are now called “satisfactory,” and a comment may be added about any obscuring factors. The category “unsatisfactory for evaluation” implies that the slide is unreadable for one of the following reasons: the slide is broken, patient identification is lacking, there is obscuration of 75% or more of the epithelial cells, or there is scant cellularity.10 Importantly, “benign cellular changes” was also eliminated as a category. These results are either shifted to the negative (no evidence of intraepithelial lesion) or the atypical squamous cells category.
Definite abnormal cells are categorized in two levels, low-grade (LSIL) and high-grade (HSIL). The original Bethesda System created a borderline abnormal category called “atypical squamous cells of undetermined significance” (ASCUS). Many experts now consider the diagnosis of ASCUS too subjective, poorly reproducible and overutilized as part of defensive medicine.10 The updated Bethesda System creates two distinct groups: atypical squamous cells-unspecified (ASC-US) and atypical squamous cells-high grade cannot be ruled out (ASC-H). The significance of the minimally abnormal Pap cannot be overemphasized, because while the majority of samples with this reading are normal, most high-grade disease is identified at the time of colposcopy in women with ASCUS and LSIL. The change from ASCUS to ASC-US and ASC-H will improve follow-up strategies that are more likely to identify women at risk.
Frequency of Screening
No clear consensus has been reached about the frequency and timing of cervical sampling. Current guidelines from the American Cancer Society and American College of Obstetricians and Gynecologists suggest that all women who are or have been sexually active, or have reached age 18, should have an annual Pap test and pelvic examination. The natural history of HPV suggests that eventually, initiation of cervical screening may be delayed a few years to allow for clearance of early HPV infection by young women. The guidelines also suggest that at the discretion of a provider, the Pap test may be performed less frequently after three consecutive normal results. Additionally, it is important to understand the low risk for CIN in virginal women and postpone screening cytology if there would be difficulty obtaining a sample from the cervix without significant physical or emotional discomfort. It is important to clarify terms, however, since a woman who reports no history of intercourse may have had HPV exposure from skin-to-skin contact.
There is no evidence that cytologic screening of the vagina for benign disease in women who have had a hysterectomy yields significant vaginal pathology. A large body of evidence suggests that woman who have had a total hysterectomy for benign disease do not need further Pap smear testing.10 A thorough history should determine the reason for hysterectomy. A woman who had pre-invasive cervical disease before hysterectomy could persist with high-risk HPV in the vagina. Although the risk for vaginal neoplasia is low in such a woman, she should continue lifetime vaginal screening. The literature contains reports of invasive cancers buried in the vaginal vault of women who have had hysterectomy after a previous history of CIN.
Supracervical hysterectomy is more common today, and women with a remaining cervix should still be screened. Many women who undergo this procedure are unaware that they still have a cervix and may falsely believe they do not need an annual Pap examination.
Conventional Cytology
The conventional Pap smear involves using a spatula and endocervical brush to obtain a cervical sample and immediately fixing it on a slide. The collection should not be taken during the menstrual period. The patient should avoid vaginal medications, vaginal contraceptives and douches during the 48 hours before the appointment. Intercourse is not recommended on the night before or the day of the exam. Use of both the Ayre spatula and the endocervical brush results in the best quality sample. The spatula should be used first to minimize blood in the sample. Both sides of the spatula should be scraped on one side of a properly labeled slide, and the cytobrush sample should be carefully rolled onto the second half of the same slide. A fixative should be applied immediately to avoid air-drying artifact.
The conventional Pap smear has a low level of sensitivity (negative predictive value) with reports of false negative smears as high as 50%. However, it has been the gold standard for the last 50 years.
Liquid-Based Cytology
The liquid-based cervical sample is collected and immediately placed into a vial of liquid. In the laboratory, a slide is prepared in a monolayer to create a visually cleaner background with less clumping of cells. With a conventional smear, 80% of the cellular material stays behind on the brush. The liquid-based sample provides more cells and a more representative sample than the conventional Pap. Liquid-based cytology was developed to address the five major limitations posed by the conventional Pap smear: failure to capture the entire specimen; inadequate fixation; random distribution of abnormal cells; obscuring elements; and technical variability in the quality of the smear.10 Two liquid-based cytologic tests are available, ThinPrep (Cytyc Corporation) and Autocyte (Tripath Corporation). Studies show that liquid-based cytology produces a higher detection rate of SIL and fewer unsatisfactory specimens than the conventional Pap smear.17
The ThinPrep sample is obtained with a plastic spatula turned on the ectocervix and followed by a brush sample of the endocervical canal. The brush and spatula should be vacillated vigorously against the sidewall of the collection vial, and the spatula can be used to scrape down cells off the brush. The Autocyte sample is obtained with one-brush sampling of the endocervix and the ectocervix. The whole brush is disconnected from its handle and dropped into the vial. If passing the brush into the cervical canal is difficult, a cytobrush sample may be additionally obtained and those cells added to the vial.
Adjunctive Testing
Screening for cervical cancer by cytology is a successful means of cancer prevention. Yet the Agency for Health Care Policy and Research (AHCPR) recently concluded that, in unbiased studies, the actual sensitivity of the Pap smear is approximately 51%.18 The use of adjunctive tests along with the Pap increases the sensitivity of finding disease, research shows.
Direct visualization of the cervix by screening colposcopy is prohibited from widespread use by cost and lack of skilled colposcopists. Visual methods have been developed as an adjunct to the Pap test. These methods evaluate the cervix by appearance of the cervical epithelium.
Cervicography
The cervigram is a photo of the cervix taken after the application of 4% vinegar at the time of a screening exam. The provider uses a Cerviscope camera to take a photo of the cervix after the Pap sample is obtained. This camera has a fixed focal length and is focused by moving the instrument back and forth. The film is sent to the National Testing Laboratory (NTL), where expert colposcopists read the cervical screening photos and generate a report. The test results may be reported in one of four categories: negative, atypical, positive and technically defective.
Adjunctive use of cervicography may increase the identification of significant cervical disease. The test can allow visualization of lesions that are missed by the cytologic screen. This colpophotograph can identify women who need additional follow-up or colposcopic evaluation. It should be used as an adjunct to Pap testing, not as a stand-alone test. A positive evaluation means that a lesion is visible, and colposcopy is recommended. It can also mean that no definite lesion is visible but that the appearance of the cervix warrants colposcopy to rule out significant disease.10,19
The cervigram has been used extensively in colposcopic education, chart documentation and monitoring of colposcopy skills. Cervicography is a valuable research tool for documentation, for teaching colposcopy recognition skills, and in the testing and monitoring of colposcopic skills.10
Speculoscopy
Speculoscopy is a visual evaluation of the cervix using a chemoluminescent light source, the Speculite. Testing materials are sold under the name PapSure. Speculoscopy visualizes the cervix with blue-white chemiluminescent illumination and low-power, portable magnification following the application of dilute acetic acid. It is the only in-office direct visual cervical exam approved by the FDA for use in all women undergoing Pap smear. Studies show that PapSure improves cervical screening to 90% detection of abnormalities, compared to 51% for the Pap smear alone. Some studies report a 99.2% negative predictive value for cervical abnormalities. In a recent study, 65% of high-risk women with negative Pap smears and positive speculoscopy had cervical dysplasia confirmed by biopsy.20,21
Speculoscopy is not currently covered by insurance. In addition to informing appropriate patients about its availability, providers must obtain patient agreements that they are willing to absorb the additional cost of this test. The manufacturer, Watson Diagnostics, provides patient payment forms, report forms and extensive patient education materials.
HPV DNA Testing
HPV cannot be cultured and must be detected through molecular techniques. The method used in clinical practice today is the Hybrid Capture 2 (marketed as HC 2 by Digene Corporation). The test is an in vitro solution hybridization, signal amplification-based test for detecting DNA and RNA targets.
It is a cocktail of low-risk and high-risk types reported as negative or positive. At this time, the testing and reporting of low-risk HPV types is not recommended and no management strategies utilize this information. There is no FDA approval at this time for polymerase chain reaction testing of cervical samples.
The HC 2 test improved its sensitivity 10 times from its first generation test by increasing high-risk probes and lowering the detection limits for HPV DNA.
The sample for DNA testing may be collected using a separate brush turned in the cervical canal and sent to the lab in a provided tube. The tube may be held at room temperature for 2 weeks while awaiting Pap results. One of the most important adjuncts to liquid sampling is the ability to obtain HPV DNA results from the residual liquid of the PreservCyt solution. This means that in the appropriate situation, a test may be obtained without an additional office visit. (At press time, ThinPrep was the only technology with FDA approval for HPV DNA residual testing, but Autocyte was pursuing FDA clearance for this use.) When a ThinPrep sample is interpreted as ASC-US, the lab can perform an HPV test for high-risk types–provided that a prior agreement has been made with the submitting provider. This is known as reflexive testing. In settings where Thin Prep is not available, the co-collected sample can be sent to the lab if the screening Pap is reported as ASC-US.
Immediate HPV-based triage of ASCUS Pap smears has a sensitivity of 90% to 96%, compared with 75% to 85% for the repeat Pap smear.21 The median sensitivity of HPV testing for routine screening of women with CIN 2 or CIN 3 and cancer is 93%, compared with 75% for the Pap smear. The Pap smear is slightly more specific than HPV DNA testing when looking for high-grade cervical disease in ASC-US management.10
Due to the high level of specificity in an HSIL result, the source of the precancerous cells must be found. If colposcopy is satisfactory and no lesion is visible, a “second opinion” pathologist should review the Pap results. In the case of unsatisfactory colposcopy in which the SCJ is up in the canal and not visualized, an excisional procedure would be required to look for disease in the canal. A high-risk positive HPV test result is common in women who do not have a defined cervical lesion. The specificity (positive predictive value) for finding high-grade disease in high-risk positive women increases with age. The high-risk positive woman who is older than 30 is more likely to have persistent HPV.
ASCUS/LSIL Triage Study
The ASCUS/LSIL Triage Study (ALTS) compared the sensitivity and specificity of the three management strategies to detect high-grade cervical intraepithelial neoplasia (CIN 3) in women referred with ASCUS or LSIL results: immediate colposcopy (considered to be the reference standard); triage to colposcopy based on HPV results from HC 2 and thin-layer cytology results; and triage based on cytology results alone. The randomized, multicenter clinical trial of women with low-grade and equivocal cervical cytology validated the use of HPV DNA testing by HC 2 as a sensitive way to detect significant cervical cancer precursor lesions.22
The management of ASCUS (now ASC) has always been controversial. Many providers have underestimated the potential danger in this Pap reading. Although less than 10% of women with this diagnosis have a high-grade SIL or invasive cancer, the majority of women ultimately found to have high-grade disease are referred with an ASCUS Pap.5 It is important to identify women in this group. Testing for high-risk HPV as a triage strategy identifies women with potential risk for disease. An important finding of ALTS, which supported previously reported data, was the high prevalence of high-risk HPV DNA in women with LSIL as their referral Pap. The HPV triage arm for women referred with a cytologic diagnosis of LSIL was closed early because an interim analysis showed that 83% of these women would be triaged to colposcopy based on a positive HPV result. This confirmed the high percentage of women with LSIL who have cancer-associated HPV types. This means that identifying the HPV DNA status of women with a screening cytology of LSIL does not offer any help in making management decisions. The majority will be high-risk positive. The additional test will not significantly alter the number of women triaged to colposcopy.22
One of the primary benefits of liquid-based cytology is the ability to obtain reflexive testing off the residual sample from the Pap. This allows for determination of HPV status as a triage for colposcopy without incurring the cost of an additional office visit. This strategy is more cost-effective at finding cancer precursors than accelerated repeat Pap or universal colposcopy. With accelerated repeat Pap, data suggesting it is more cost-effective than HPV testing is misleading because the number of women who eventually go to colposcopy after a second abnormal Pap is high. Additionally, repeat Pap data does not always represent true cost, since follow-up cost data is affected by the number of women who are lost to follow-up and are no longer included in subsequent cost analysis.2,5
Consensus Guidelines
Newer understanding of the natural history of HPV and cervical cancer precursors and new technologies (including HPV DNA testing) contributed to the need for the development of evidence-based guidelines for practice. To address these issues and to revise Bethesda System reporting of cytologic abnormalities, experts met in 2001. Under the direction of the American Society for Colposcopy and Cervical Pathology (ASCCP), 121 invited participants from 29 organizations came together to develop guidelines. Draft guidelines were posted on Internet bulletin boards for public comment. The final guidelines were published in the Journal of the American Medical Association on April 24, 2002.2 The guidelines are available online at www.asccp.org.
These recommendations are most significant for the management of minimally abnormal Pap smears. Evidence reported in the ALTS study supported the decisions regarding ASC-US and LSIL. The current recommendation for ASC-US has been to decide among the options of accelerated repeat Pap, universal colposcopy or HPV DNA testing. Each of these approaches has advantages and disadvantages.
The consensus committee of the ASCCP states that a program of repeat cervical cytological testing, colposcopy or DNA testing for high-risk types of HPV are all acceptable methods for managing women with ASC-US.2 When liquid-based cytology is used or when co-collection for HPV DNA testing can be done, reflexive HPV DNA testing is the preferred approach. Reflexive HPV DNA testing or co-collected and held samples offer significant advantages since women do not need an additional clinical examination for specimen collection.2,23
DNA testing for high-risk HPV should be done with a sensitive molecular test, and all women who test positive should be referred for colposcopy. Women who test negative should be followed up with a repeat Pap at 12 months. The recommended management for ASC-H is immediate referral for colposcopy, since there is a significant amount of high-grade disease with this diagnosis . Because the ALTS trial showed that the majority of women with LSIL are positive for high-risk HPV, there is no evidence to support HPV triage for LSIL. The guidelines recommend that all women with ASC-H results be referred for colposcopy. Additionally, the guidelines recommend colposcopy for all women with LSIL.
The finding of atypical glandular cells of undetermined significance (AGUS) has been renamed AGC to avoid confusion with ASC-US. This cytologic category requires an aggressive response including colposcopy, endocervical curettage (ECC) and endometrial evaluation in women older than 40. There is a significant risk for adenocarcimona in women with this Pap reading. There is no consensus on the use of HPV testing as a triage strategy in this group.
Screening of Women Over 30
The FDA recently approved the use of Hybrid Capture 2 for primary screening of women older than 30. HPV testing is not an effective test in young women with transient HPV infections.10 For women younger than 30, the Pap smear continues to be an important, albeit imperfect, tool. Even in areas where cervical cancer screening by Pap is available, cervical cancer has not been eliminated. Many women never seek screening due to multiple factors, including lack of insurance, lack of information and fear of the exam. Some patients and providers never act on abnormal results. A false-negative rate is inherent in Pap testing due to sampling and interpretive errors.24
It is important to consider the natural history of HPV and the frequency with which it is diagnosed in the young, sexually active population. Screening of women younger than 30 by HPV DNA alone would identify too many who are infected with the high-risk types of HPV and do not have a precursor lesion on the cervix. The test has low specificity in young women, but the specificity increases with age. In women older than 30, a positive HPV DNA has greater positive predictive value for the presence of SIL (high specificity).5,25 Women who are positive for high-risk HPV but have no disease are actually not true false-positives. They are at greater risk for cervical intraepithelial neoplasia unless they clear the virus. HPV DNA screening in an older age group would postpone testing for HPV positivity, allowing for a possible immune response and subsequent clearance of the virus. This would provide identification of women who are high-risk HPV persistent and at greater risk for significant cellular abnormality.
Uses for HPV DNA testing are being identified and developed. One use may be in screening older women to identify those who are negative for high-risk HPV. Identifying women who are HPV DNA-negative may allow for widening of screening intervals. Self-sampling for HPV with a vaginal swab is also subject of study.
Future use of HPV testing may involve self-sampling by women who are unwilling to have invasive Pap testing, or by women treated in settings where Pap testing is not available. This would not reduce the need for annual screening for other women’s health concerns.26
Patient Counseling
HPV DNA testing will continue to increase as providers become more familiar with the test and its applications. The ASCCP Consensus Guidelines name reflexive testing for high-risk HPV the preferred strategy for management of the borderline abnormal Pap.2 This means that many women will find out about their positive HPV status at the same time they receive an abnormal Pap test result. It is imperative, then, to teach women about HPV early in their health care experience. Education about HPV should start at the onset of a women’s cervical cancer screening. Most importantly, women should understand that high-risk HPV is common, is the most common type in young women with mild abnormal cells, and usually does not cause cancer.
HPV is primarily transmitted through genital-to-genital contact. When one partner has HPV, it is likely that the other partner shares the same type. Several studies show that the virus does not “ping-pong” back and forth.27 The outcome after exposure to any type of HPV is dependent on a person’s own immune response to that exposure and not re-exposure to a partner. Being exposed to more of the same viral type of HPV does not appear to alter the ability to clear one’s own disease.6,27 This means that couples cannot re-infect each other within their own relationship. If a person enters a new relationship, he or she could put a new partner at risk until known lesions are cleared. However, a person can be exposed to a new viral type of HPV with a new partner. When a woman has active condylomatous disease, more viral shedding occurs than when she is clear of the active disease. After clearance of warts, a decreased chance of passing the virus is likely.
There is no way to be 100% sure that a patient is no longer contagious, and communication with a new partner about HPV is advisable. This information should be discussed with an understanding that the majority of people who have been sexually active have been exposed to HPV. The usual outcome after exposure to HPV is no knowledge of the exposure and no active disease expression. After exposure to HPV and subsequent clearance of detectable DNA levels, a patient probably has immunity to that type. He or she can’t be re-infected, but could be exposed to a new type.
An area of great research interest is the development of HPV vaccines for important oncogenic types. Many clinical issues remain to be determined, including deciding who would benefit from vaccination and at what age. Vaccines may play a role in offering protection to high-risk unscreened populations.28
It is important to advise patients that a finding of HPV does not necessarily mean the infection is new. Women tend to be concerned that a positive test may reflect infidelity by their current partner. We can never know when the exposure occurred or whether it is from a current partner. Most people become HPV-negative on the same test within 6 to 24 months after the first positive result. Although persistence is necessary for significant disease to develop, a high-risk positive result in a woman in a long-term relationship does not mean that she will develop a serious problem.
Abstinence is the only way to avoid transmission of HPV. This includes abstinence from intercourse with penetration as well as abstinence from genital-to-genital or hand-to-genital touching.6 It is not reasonable or necessary to recommend permanent sexual abstinence. It is helpful to focus on HPV education as an issue of cancer prevention rather than STD prevention. We must encourage all women to obtain appropriate screening and follow-up. We must educate all people that HPV is a common virus usually cleared by an immune response. If we utilize HPV testing, we must be able to communicate the finding of high-risk positivity as a risk factor that does not constitute a cause of cancer by itself. The woman at greatest risk is the woman who is high-risk HPV-positive, has viral persistence and does not receive screening.
Nurse practitioners are in an ideal position to offer quality education about HPV and cervical cancer screening to women and other health care providers. The advent of new Pap methods and adjunctive testing for HPV are the most important changes in cervical cancer screening in 50 years. The changes may help reduce cervical cancer and the costs of screening, but will increase the need for HPV education and understanding by all who participate in providing and receiving this care.
References
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Nancy Berman is an adult nurse practitioner and colposcopist who provides women’s health care at Northwest Internal Medicine Associates in Southfield, Mich., a division of Millennium Medical Group. She is a member of the practice committee of the American Society for Colposcopy and Cervical Pathology and is a recipient of the organization’s Colposcopy Recognition Award, an expert designation. Berman is also a member of the speakers’ bureaus for Cytyc, Digene and Tripath.
