HPV self-sampling in cervical cancer screening: the effect of different invitation strategies in various socioeconomic groups - a randomized controlled trial.

Background: Participation in cervical cancer screening varies by socioeconomic status. The aims were to assess if offering human papilloma virus (HPV) self-sampling kits has an effect on screening participation among various socioeconomic groups and to determine if two invitation strategies for offering self-sampling influence the participation rate equally.

Methods: The study was based on registry data that were applied to data from a randomized controlled trial (n=9,791) measuring how offering HPV self-sampling affected screening participation. The women received either 1) a self-sampling kit mailed directly to their homes (directly mailed group); 2) an invitation to order the kit (opt-in group); or 3) a standard second reminder to attend regular cytology screening (control group). The participation data were linked to registries containing socioeconomic information.

Results: Women in the directly mailed group participated significantly more than women in the control group, regardless of their socioeconomic status, but the largest effects were observed in Western immigrants (participation difference [PD]=18.1%, 95% CI=10.2%-26.0%) and social welfare recipients (PD=15.2%, 95% CI=9.7%-20.6%). Compared with the control group, opt-in self-sampling only had an insignificant effect on participation among women who were immigrants, retired, or less educated. Western immigrants had a significantly higher increase in participation than native Danish women when kits were mailed directly compared with the opt-in strategy (PD=18.1%, 95% CI=10.2%-26.2% and PD=5.5%, 95% CI=2.9%-8.1%, respectively, =0.01).

Conclusion: All socioeconomic groups benefited from the directly mailed strategy in terms of higher screening participation, but Western immigrants and lower socioeconomic groups seemed to benefit the most. Immigrants and some lower socioeconomic groups only had insignificant benefits of opt-in self-sampling. The directly mailed strategy might be preferable to opt-in self-sampling because it ensures that ethnic minority groups obtain benefits of introducing HPV self-sampling in an organized cervical cancer screening program.

Trial Registration: Current Controlled Trials NCT02680262. Registered February 10, 2016.