To assess CIN2+ risks by HPV16/18 genotyping or reflex cytology in prevalent and incident screen-detected high-risk HPV (hrHPV) infections.
Data from women participating in the randomized Population Based Screening Study Amsterdam (POBASCAM) were used. Women with a prevalent hrHPV infection at baseline and women with an incident hrHPV infection at the second screen – occurring 4 to 9 years after enrolment – were included in the analysis. The age-range at testing was 34-60 years for both groups. Histology results occurring within 14 years after enrolment were obtained. The cumulative risks of CIN2+ were estimated by Kaplan Meier.
Among 730 women with a prevalent hrHPV infection, 217 CIN2+ cases were detected during follow-up (mean 9.0 years; range 0.02-14 years), resulting in a cumulative risk of CIN2+ of 21.2% after four years and of 29.1% after nine years. Among 490 women with an incident hrHPV infection, 94 CIN2+ cases were detected during follow-up (mean 6.0 years; range 0.04-10.0). The corresponding cumulative risk of CIN2+ was 15.4% after four years and 21.3% after nine years.
Risk-stratification by HPV16/18 genotyping of a prevalent hrHPV infection identified women with a 45.5% cumulative CIN2+ risk after nine years, compared to a 20.3% CIN2+ risk among HPV16/18-negative women. The difference in CIN2+ risks nine years after an HPV16/18-positive and HPV16/18-negative incident infection was less pronounced (24.8 versus 19.6%, respectively). Reflex cytology was a strong CIN2+ risk-stratifier for both prevalent hrHPV infections (abnormal cytology: 62.4% versus normal cytology: 15.7%) and incident hrHPV infections (abnormal cytology: 44.9% versus normal cytology: 14.4%).
We have observed that risk triaging of hrHPV-positive women yields different results for prevalent and incident hrHPV infections. This emphasizes the important role of infection duration when defining screening and triage algorithms.