Developments that radically change cervical cancer screening
Until recently exfoliative cytology formed the basis for cervical cancer screening and to a major extent fulfilled the criteria defined many years ago for an effective method of screening . Its success has been demonstrated in many countries during the past 50 years ; but recent developments in HPV technology including vaccination have radically changed cervical cancer screening.
- Discovery of high-risk types of HPV as the main aetiological agent for cervical cancer and its precursors
- Development of vaccines against the most frequent oncogenic types of HPV
In countries where uptake of vaccination is high this will dramatically reduce the incidence of HPV-related precancerous lesions and cancer. Primary HPV testing is being introduced in various countries with or without cytology co-testing as a result of which the role of cytology will change substantially in the years to come. Nevertheless, in many countries and centres cytological screening with conventional Pap smears remains the primary screening test.
- In many countries cytological screening remains the primary screening test.
- The principles of cytological screening are essentially unchanged by their integration with HPV testing and vaccination.
- The importance of accuracy of cervical cytology would be enhanced in samples known to be HPV-positive submitted for cytology triage.
Cervical cytology provides, without damage to the underlying tissue, a cellular sample of the entire transformation zone (TZ) of the cervix where most precancerous lesions develop . When samples are taken for liquid-based cytology it provides a medium on which HPV testing and other molecular tests can be carried out. HPV testing is frequently used for triage of atypical or borderline cytology and as a test of cure after treatment of high-grade precancerous lesions.
Although cytological diagnoses may be supported by colposcopically directed punch biopsies, the final diagnosis depends on histological examination of the entire TZ either by large loop excision or cone biopsy.
Alternative methods of cervical cancer screening
The WHO guidelines for cervical cancer screening only recommend cytological screening “in countries where an appropriate/high-quality screening strategy with cytology followed by colposcopy already exists”, where “either an HPV test or cytology followed by colposcopy could be used.”
All other options include various combinations of HPV testing, visual inspection with acetic acid (VIA), colposcopy and treatment in preference to cytological screening (WHO 2013).
This Eurocytology teaching programme is designed for countries and centres where cervical cytology is already in place
It is primarily aimed at training new recruits in screening and reporting cytology
It also aims to update existing practitioners including those working in other professions involved in screening programmes
Everything you need to know about HPV testing
Cytological screening increasingly requires integration with HPV testing in at least one or other of the settings below. For a comprehensive overview of the uses and challenges presented by HPV testing, see the review by Cubie & Cuschieri 2013. For a meta-analysis of all types of HPV tests see Arbyn et al. 2012.