Is it rational to start population-based cervical cancer screening at or soon after age 20? Analysis of time trends in preinvasive and invasive diseases.

The effect of starting screening at age 20 in 1988 was assessed by analysing (a) the age-specific incidence and distribution of stage and histology of invasive diseases, and (b) the detection rates of histologic moderate to high-grade intraepithelial neoplasia (CIN 2-3/AIS), and 1st abnormal cytology and repeat low-grade cytology after follow-up observation. Cancer incidence increased significantly at age 25-34 after 1979 due to early stage squamous cell and adenocarcinoma. After an initial increased rate of preinvasive disease, CIN 3 decreased significantly at age 30-34 after 1988, at age 25-29 after 1993, and levelled out after 1998 at age 20-24. The rates of CIN 2 levelled out after 1998. The rates of repeat low-grade smears decreased after observation at age 20-24 by 80%. The study confirms an increasing rate of preinvasive and invasive disease among younger women and indicates the benefit of starting organised screening at 2-3 year intervals soon after age 20.