HPV screening performance indicators in women who previously tested HPV-negative: The second round of Vallecamonica screening programme, Northern Italy

To present performance indicators from the second round of the Vallecamonica-Sebino HPV screening programme in women who had tested negative about four years earlier (mean 45 months).

From 2010 to 2012, the target female population (aged 25-64) was invited to the first HPV screening round. In 2013-2017, women were rescreened for the second round. HPV-negative women at the first round were initially rescreened after three years. The interval was gradually increased to five years. HPV-positive women underwent cytology triage: positives were referred to colposcopy and negatives to repeat testing after one year. If HPV was persistently positive, women were referred to colposcopy, if negative, to normal interval rescreening.

In the second round, of 13,824 previously HPV-negative women, 598 were HPV-positive (4.3%), of whom 297 were positive at cytology triage. Of those referred to one-year HPV test, 291 complied (98.0%), 133 (50.2%) of whom were persistently positive. Total referral was 3.1% compared with 6.6% in the first round (age-adjusted relative referral 0.59, 95% CI: 0.53-0.65). There were 24 cervical intraepithelial neoplasia 2+ (three cervical intraepithelial neoplasia 3+). Detection was 0.17%, compared with 0.9% in the first round. Age-adjusted relative detections were 0.25 (95% CI: 0.16-0.39) and 0.18 (95% CI: 0.05-0.61) for cervical intraepithelial neoplasia 2+ and cervical intraepithelial neoplasia 3+, respectively. Positive predictive value was 5.7%, compared with 14.6% in the first round.

At second round, referral was half that at first round, while cervical intraepithelial neoplasia 2+ detection decreased nine-fold. Consequently, positive predictive value decreased dramatically. Rescreening four years after an HPV-negative test makes the process inefficient due to the low prevalence of lesions.