Referral population studies underestimate differences between human papillomavirus assays in primary cervical screening

Predictable changes in the accuracy of human papillomavirus tests after vaccination: review with implications for performance monitoring in cervical screening

Vaccination against human papillomavirus (HPV) is changing the performance of cytology as a cervical screening test, but its effect on HPV testing is unclear. We review the effect of HPV16/18 vaccination on the epidemiology and the detection of HPV infections and high-grade cervical lesions (CIN2+) to evaluate the likely direction of changes in HPV test accuracy. The reduction in HPV16/18 infections and cross-protection against certain non-16/18 high-risk genotypes, most notably 31, 33, and/or 45, will likely increase the test's specificity but decrease its positive predictive value (PPV) for CIN2+. Post-vaccination viral unmasking of non-16/18 genotypes due to fewer HPV16 co-infections might reduce the specificity and the PPV for CIN2+. Post-vaccination clinical unmasking exposing a higher frequency of CIN2+ related to non-16/18 high-risk genotypes is likely to increase the specificity and the PPV of HPV tests. The effect of HPV16/18 vaccination on HPV test sensitivity is difficult to predict based on these changes alone. Programmes relying on HPV detection for primary screening should monitor the frequency of false-positive and false-negative tests in vaccinated (younger) vs. unvaccinated (older) cohorts, to assess the outcomes and performance of their service.

Staged design recommendations for validating relative sensitivity of self-sample human papillomavirus tests for cervical screening

OBJECTIVES

To ensure that the emerging methods for human papillomavirus (HPV) testing on self-collected samples in cervical screening are evaluated robustly.

STUDY DESIGN AND SETTING

We assess paired study designs for relative sensitivity of self-collected vs. traditional clinician-collected samples in detection of high-grade cervical intraepithelial neoplasia.

RESULTS

Designs considered are (D1) both samples at screening, with clinical actions triggered by HPV positivity; (D2) offering a self-sample test to clinician-collected HPV-positive women; (D3) as D2 but using a repeat clinician-sample as comparator; (D4) offering a choice of self- vs. clinician-sampling, and the alternative test in HPV-positive women; (D5) paired samples at referral appointment. D1 is simple to analyze but requires the largest sample size and referral of self-sample positive, clinician-sample negative women. D2 requires a much smaller sample size, and no change to clinical practice, and could be used to rule-in a test because estimates are conservative (against self-sampling). D3 mitigates this bias but requires a second clinician sample. D4 is only manageable where self-sampling already occurs. The liberal D5 might be used to rule-out a self-sampling test.

CONCLUSION

A universal recommendation for an optimal study design is challenging. Staged validation might be useful with D5 as a gatekeeper for D1-D4.

Widening the offer of human papillomavirus self-sampling to all women eligible for cervical screening: Make haste slowly

Self-collection of samples for human papillomavirus (HPV) testing has the potential to increase the uptake of cervical screening among underscreened women and will likely form a crucial part of the WHO's strategy to eliminate cervical cancer by 2030. In high-income countries with long-standing, organised cervical screening programmes, self-collection is increasingly becoming available as a routine offer for women regardless of their screening histories, including under- and well-screened women. For these contexts, a validated microsimulation model determined that adding self-collection to clinician collection is likely to be cost-effective on the condition that it meets specific thresholds relating to (1) uptake and (2) sensitivity for the detection of high-grade cervical intraepithelial neoplasia (CIN2+). We used these thresholds to review the 'early-adopter' programme-level evidence with a mind to determine how well and how consistently they were being met. The available evidence suggested some risk to overall programme performance in the situation where low uptake among underscreened women was accompanied by a high rate of substituting clinician sampling with self-collection among well-screened women. Risk was further compounded in a situation where the slightly reduced sensitivity of self-sampling vs clinician sampling for the detection of CIN2+ was accompanied with lack of adherence to a follow-up triage test that required a clinician sample. To support real-world programmes on their pathways toward implementation and to avoid HPV self-collection being introduced as a screening measure in good faith but with counterproductive consequences, we conclude by identifying a range of mitigations and areas worthy of research prioritisation.

Human Papillomavirus Testing in the Last Cervical Screening Round at Age 60-64 Years

OBJECTIVE

To compare the real-life screening outcomes after cytology was replaced by human papillomavirus (HPV) testing for women aged 60-64 years.

METHODS

Using the Danish national pathology register, we compared screening outcomes during two consecutive calendar periods, one where women were screened with cytology and one where most women were screened with HPV testing. Our primary outcomes were the proportions of women with positive test results, high-grade cervical intraepithelial neoplasia (CIN 2 or worse), and cervical cancer.

RESULTS

Women screened during the HPV testing period were more likely to have a positive screening test result than were women screened during the cytology period (relative proportion 2.80, 95% CI 2.65-2.96). The detection of CIN 2 or worse was also increased (relative proportion 1.54, 95% CI 1.31-1.80), whereas there was no increase in screen-detected cervical cancer diagnoses (relative proportion 1.27, 95% CI 0.76-2.12). Within the first 4 years after a negative screening test result, including 168,477 woman-years at risk after a negative screen result in the HPV period and 451,421 woman-years after a negative screen result in the cytology period, the risk of a cervical cancer diagnosis was approximately 4 per 100,000 woman-years and was similar for both screening tests (relative risk 0.99, 95% CI 0.41-2.35).

CONCLUSION

Human papillomavirus testing led to more positive screening test results and diagnoses of high-grade CIN lesions. Few women were diagnosed with cervical cancer after a negative screening test result.

Cervical Cancer Screening Programs in Europe: The Transition Towards HPV Vaccination and Population-Based HPV Testing

Cervical cancer is the fourth most frequently occurring cancer in women around the world and can affect them during their reproductive years. Since the development of the Papanicolaou (Pap) test, screening has been essential in identifying cervical cancer at a treatable stage. With the identification of the human papillomavirus (HPV) as the causative agent of essentially all cervical cancer cases, HPV molecular screening tests and HPV vaccines for primary prevention against the virus have been developed. Accordingly, comparative studies were designed to assess the performance of cervical cancer screening methods in order to devise the best screening strategy possible. This review critically assesses the current cervical cancer screening methods as well as the implementation of HPV vaccination in Europe. The most recent European Guidelines and recommendations for organized population-based programs with HPV testing as the primary screening method are also presented. Lastly, the current landscape of cervical cancer screening programs is assessed for both European Union member states and some associated countries, in regard to the transition towards population-based screening programs with primary HPV testing.