HPV vaccination and effects on screening
Dr. Paola A. Gehrig
Currently, given that the HPV vaccines available do not protect women from all oncogenic HPV types, the ASCCP, USPSTF, and ACOG all recommend screening vaccinated women in an identical fashion to unvaccinated women. Increasing vaccination rates will likely have an impact on the efficacy of the various cervical cancer screening modalities. Vaccination will result in a reduction in the prevalence of cytologic abnormalities. As disease prevalence decreases and screening intervals increase based on current guidelines, the positive predictive value of Pap cytology also will decline, resulting in more false-positive diagnoses and possibly unnecessary procedures and patient stress (Vaccine 2013;31:5495-9). As prevalence of disease decreases, Pap cytology has the potential to become less reliable. While the positive predictive value of HPV testing also declines with decreasing disease prevalence, HPV testing is more reproducible than interpretation of Pap cytology, so the extent of increasing false-positive results may be less (Vaccine 2006;24 Suppl 3:S3/171-7).
Future directions
HPV testing as primary screening for cervical cancer is not currently recommended. However, in the post-HPV vaccination era, this may become an increasingly reasonable approach, particularly in conjunction with Pap cytology used to triage patients who test positive for high-risk HPV subtypes. HPV testing has much greater sensitivity than Pap cytology does and can better identify patients who are likely to have a cytologic abnormality. In this group of patients with greater disease prevalence, the slightly higher specificity of Pap cytology can then be used to identify precancerous lesions and guide treatment. Once this group of patients with higher lesion prevalence than the general population has been identified through HPV testing, Pap cytology can then be used and will perform better than in a lower prevalence population.
The importance of Pap cytology and HPV testing in cervical cancer screening continues to evolve, particularly in the current era of HPV vaccination. The combination of HPV testing followed by Pap cytology has potential for becoming a highly effective screening strategy; however, the optimal administration of these tests is yet to be determined. As current screening modalities improve and new technologies emerge, ongoing work is needed to identify the most effective screening method for cervical cancer.
Dr. Wysham is currently a fellow in the department of gynecologic oncology at the University of North Carolina at Chapel Hill. Dr. Kim is the department of gynecologic oncology at UNC-Chapel Hill. Dr. Gehrig is professor and director of gynecologic oncology at UNC-Chapel Hill.