Repeat Invitations and Participation in Cervical Screening: A Population-Based Cohort Study.

ObjectiveCervical cancer screening reduces incidence and mortality dependent on participation. To increase participation we investigated the best time to send repeated invitation (RI) letters to those who did not attend screening after the first letter.MethodsWe designed a prospective population-based cohort study featuring 3,352,211 first invitation letters and 2,449,187 RI letters sent between 2012-01-01 and 2023-12-31 to all Swedish screening-eligible women aged 23 to 70. We measured participation rates based on the time between invitation letters and their first RIs, adjusted for age, calendar month/year, screening test (HPV/cytology), and healthcare region.ResultsThe strongest RI-to-participation association was observed for RIs sent 8-12 weeks after the invitation letter, with 65% participation and adjusted odds ratio (aOR) 1.42 (1.34-1.50). This was consistent for women below 50, aOR 1.35 (1.28-1.44) / 64% participation; and women above 50, aOR 1.95 (1.63-2.32) / 72% participation. Participation declined with number of RIs sent, with the first RI followed by 49% participation and the seventh followed by 21% participation. Only 10.9% of the screening population required a fourth RI or more.ConclusionSending a RI 8-12 weeks after the original invitation was associated with the highest participation. After sending four RIs other methods of communication should be employed to encourage screening participation.