A quasi-randomized trial on the effectiveness of an invitation letter to improve participation in a setting of opportunistic screening for cervical cancer.

The objective of the study was to assess the effect of an invitation letter on the level of participation in a setting of mainly opportunistic screening for cervical cancer and to do a cost analysis of this intervention. We designed a quasi-randomized trial in which a sample of women between the ages of 25 and 64 years and residing in the province of Limburg, Belgium, who had no Pap smear taken in the past 30 months according to LIKAR (Limburg Cancer Registry), were assigned to an intervention group or to a control group. A written invitation was sent to 43 523 women in the intervention group.