Effect of regular 3-yearly screening on the incidence of cervical smears: the Leiden experience.

The effect of regular 3-yearly screening over a period of 12 years, on the incidence of cervical cancer in 25,000 women aged 35-54 years, is examined. The rate of squamous cell carcinoma decreased from 0.38 per 1000 women in the first round to zero in the fourth round. Similarly, the rate of carcinoma in situ declined from 1.69 per 1000 women in the first round to 0.35 per 1000 in the fourth round. The rates of severe dysplasia showed no decline. Cytologic under diagnosis of carcinoma-in-situ and cervical carcinoma increased with each round. Widowed and divorced women and those living in urban areas were identified as high risk groups.