Long-term follow-up of cervical abnormalities among women screened by HPV testing and cytology-Results from the Hammersmith study.

Several studies have shown that HPV testing is substantially more sensitive than cytology for primary cervical screening. However, less data exist concerning the duration of protection afforded by a negative HPV test compared to a normal cytological outcome. Here we report the long-term findings from the Hammersmith study in women aged 35 or more. HPV testing by Hybrid Capture II was performed on all available samples from the baseline screening visit. Passive surveillance of subsequent cytology screening results for the 2,982 women in the study was undertaken using a national registry. Histological outcomes were sought for all women with abnormal smears. The primary outcome was duration of protection against histologically confirmed CIN2+ afforded by a negative HPV test compared to normal cytology. 2,516 women had at least one further smear at least 1 year after entry and 20 new cases of CIN2+ were identified during a median follow-up of 6.4 years. Including disease identified at baseline, the risk of developing CIN2+ at 1, 5 and 9 years after a normal cytology was 0.33%, 0.83% and 2.20% respectively whereas it was 0.19%, 0.42% and 1.88% after a negative HPV test. HPV testing offered excellent protection from CIN2+ for at least 6 years after a negative test, whereas the protection from cytology began to wane after about 3 years. Substantially more CIN2+ lesions were found in the follow-up period in those initially HPV positive compared to those HPV negative (HR = 6.52, p = 0.001), whereas there was little difference according to initial cytology (HR = 1.64, p = 0.51).