Distribution of high and low risk HPV types by cytological status: a population based study from Italy

BACKGROUND: HPV type distribution by cytological status represents useful information to predict the impact of mass vaccination on screening programs. METHODS: women aged from 25 to 64 who attended cervical cancer screening in five different Italian regions were tested for HPV infection with Hybrid Capture II (HCII) low and high risk probes. Women repeating Pap-test upon unsatisfactory or positive results, or as a post-treatment and post-colposcopy follow-up analysis, were excluded from our study. High risk (HR) HPV positive samples were typed using GP5+/GP6+ primed PCR, followed by Reverse Line Blot for 18 high/intermediate risk HPV types, while low risk (LR) HPV positive samples were tested with type specific primers for HPV6 and HPV11. RESULTS: 3410 women had a valid HCII and Pap-test. The prevalence of HR and LR infections was 7.0% and 3.6%, 29.1% and 13.7%, 68.1% and 31.9%, 60.0% and 0.0%, 65.0% and 12.0%, for negative, ASC-US, L-SIL, ASC-H and H-SIL cytology, respectively. The fraction of ASC-US+ cytology due to HPV 16 and 18 ranged from 11.2 (HPV 16/18 alone) to 15.4% (including HPV 16/18 in co-infection with other virus strains), and that due to HPV 6 and 11 ranged from 0.2% (HPV 6/11 alone) to 0.7% (including HPV 6/11 in co-infection with other LR virus strains). CONCLUSIONS: mass vaccination with bivalent or quadrivalent HPV vaccine would modestly impact on prevalence of abnormal Pap-test in screening.