Family doctor

A change to cervical screening (involving HPV testing)

There has been a change to the conventional cervical ‘Pap smear’ test in New Zealand. It no longer involves smearing cervical cells onto a glass slide, but instead involves the washing cells into a vial of fixative. This new process is called liquid-based cytology (LBC) but the process will still most likely remain known as a “smear test”. From the patient’s perspective, things will remain the same in that a speculum is inserted into the vagina in the usual way and then the doctor/nurse takes the sample of cells required from the cervix.

Compared with the Pap smear there were some problem situations where LBC now offers some advantage, for example, in women with:

·         excessive cervical mucus, discharge or blood

·         recurrent inflammatory smears

• recurrent unsatisfactory smears

So in summary the main advantages of LBC compared with the Pap smear are:

• Nearly all the cells collected are transferred into the vial of fixative from which a representative homogeneous smear can be made and most obscuring blood and inflammatory debris can be removed.
• There are no preparation artifacts such as air drying and multiple slides can be prepared from one sample. Also part of the sample can be used for other purposes if needed e.g. Human Papilloma virus (HPV) testing.
• If the initial preparation is unsatisfactory, the LBC vial containing the sample can be re-examined and a second slide may be prepared leading to better quality slides and so a decrease in the number of smears called “unsatisfactory”.
• With computer assisted screening it is expected that the average cytologist will be able to increase their throughput with a shorter time required for interpretation,

HPV testing

One of the advantages of LBC is the ability to use the same sample for Human Papilloma virus (HPV) testing. HPV is one of the most common sexually transmitted infections in the world. 15-20% of young sexually active women acquire genital HPV infection per year. Adolescents who are sexually active have the highest rates of HPV infection rates with over 50-80% having infections within 2-3 years of initiating sexual intercourse. Although HPV infection is common, studies suggest that approximately 90% of infections clear within 2 years with only a small proportion progressing to cervical pre-cancer and cancer.

Certain HPV types (e.g. type 16, 18, 31, 33) are associated with a higher risk of progressing to cancer, so these are known as high-risk HPV types. A cervical smear showing dysplasia, intraepithelial neoplasia or cervical cancer is almost always a result of persistent HPV infection, whereas in the absence of persistent infection with high-risk HPV types, cervical cancer is not expected to develop.

From 1st October 2009 there has been an integration of HPV testing into the cervical screening programme guidelines which identifies particular areas of management of asymptomatic women with abnormal cervical smears who may benefit from HPV testing:

• Women aged 30 years and over with atypical squamous cells of undetermined significance (ASCUS) or low grade changes (without an abnormal smear in the last five years).
• The follow-up of women who have been treated for a high-grade cervical lesion.
• Post colposcopy management of women with discordant smear results

Woman aged over 30 years with ASCUS or low grade changes

HPV testing is used to determine the likelihood of a low grade lesion progressing to high grade lesion for women over 30 years. There is clear agreement that women with high grade abnormalities should be referred to colposcopy but what is less clear is how to care for women with less severe abnormalities. The complexity of managing low-grade abnormalities relates to their mostly self-limiting nature, as well as the evidence that they can contain high grade lesions in up to 20% of cases (as a small number of cases of cervical cancer are diagnosed quite soon after low-grade cytology).

HPV testing in women over 30 years old will help in the management of these situations. A positive HPV test indicates increased risk of developing a high grade lesion, and so can be a useful adjunct to the management of abnormal cell changes seen in smears. HPV testing is not indicated in women less than 30 years of age due to the high prevalence of HPV infection in young women, the vast majority of which clear within 2 years and are of little clinical significance.

Women over 30 years of age with ASCUS or a low grade abnormality who tests positive for HPV should be referred to colposcopy. Women who are found to be HPV negative can be followed up with repeat cytology testing. Following a negative cytology result at 12 months, a woman can return to normal three yearly screening.

Follow-up of women who have been treated for a high grade lesion

Women who have been previously treated for CIN2/3 are at increased risk of further high grade disease and cervical cancer and HPV testing changes the management of these women. Following two consecutive negative smears and HPV tests, 12 months apart, the woman who has been treated for a high grade lesion will be able to return to normal three yearly screening intervals. This would then stop the need for annual smears for life for many women (which has been the usual follow-up for women previously treated for a high grade lesion).

Post colposcopy management of women with discordant smear results

Discordant results are when a smear result differs from the physical appearances seen at colposcopy e.g. high grade cytology (significantly abnormal smear result) with negative or satisfactory colposcopy. As a single colposcopic examination can miss significant lesions, HPV testing can help to clarify appropriate management. Following two consecutive negative smears and HPV tests, 12 months apart, the woman who has had a normal colposcopic examination for a previous high grade cytology will be able to return to normal three yearly screening intervals.

Resources

Ministry of Health, 2008. Guidelines for Cervical Screening in New Zealand, Incorporating the Management of Women with Abnormal Cervical Smears. National Cervical Screening Programme, Wellington, New Zealand. Available from: http://www.nsu.govt.nz/Files/NCSP/NCSP_Guidelines_ALL_small(1).pdf.

Diagnostic Medlab. Cervical Cytology. Pathology Bulletin, 2007. Available from: http://www.dml.co.nz/downloads/1547_Bulletin-Cervical_Cytology2007.pdf.

Franco EL, Villa LL, Sobrinho JP, et al. Epidemiology of Acquisition and Clearance of Cervical Human Papillomavirus Infection in Women from a High Risk Area for Cervical Cancer. The Journal of infectious diseases. 1999; 180:1415-23. Available from: http://www.journals.uchicago.edu/doi/abs/10.1086/315086.

NCSP. Review of the Guidelines for Cervical Screening in New Zealand Presentation for Smeartakers, September 2008. Available from: http://www.moh.govt.nz/moh.nsf/pagesmh/8479/$File/presentation-for-smear-takers.ppt.