Selective screening for cervical cancer. Experience of the Finnish mass screening system.

Names of women eligible to be screened for cervical cancer are taken from the national population registry and the women are invited by a personal letter. The data, from these mass screenings are analysed and stored at the screening registry. To reduced the costs of the system and to increase the yield of preinvasive lesions the idea of selective screening was considered. Tt was decided that if people were selected according to their risk factors, as recorded in the national population registry, the screening would be ineffective as many cases of invasive cancer were found in the low risk groups. High risk factors were determined from anamnestic data on systems and from previous cytological diagnoses. The proportion of women with symptoms of bleeding or the class II-V smears without positive histological results constituted fewer than 10% of the participants, but 20% and 40% respectively of invasive carcinomas were found in these groups during the subsequent follow-up period. Thus it is suggested that selective screening apart from that based on age has a limited application and should be restricted mainly to the interval between the organised screenings, which in Finland is five years.