Age at time of first intercourse v. chronologic age as a basis for Pap smear screening.

The Walton Report on cervical cancer screening programs recently recommended a new program for screening for cervical cancer based on chronologic age, calling for 3- and 5-year intervals between examinations. It recommended that such examinations be discontinued after 60 years of age. In a group of 232 routinely examined women (aged 18 to 47 years) in whom cervical intraepithelial neoplasia developed the timing of onset of the disease and the implications for screening were studied. The average age at the time of diagnosis was 30 years; in 20% of the patients the diagnosis had been made after age 35. The screening program recommended in the Walton Report would have been effective in diagnosing most cases (80%) in this sample by age 35 and all by age 60. However, when the patients were grouped according to age at the time of first intercourse, the diagnosis had been made after age 35 in only 13% of those who started having intercourse at age 15 to 17 years, 20% of those who started at age 18 to 19 years and 33% of those who started at age 20 years of later. When the times of diagnosis were expressed by number of years of intercourse the distributions became uniform in the same three groups; in 72% of all the patients the diagnosis had been made within the first 15 years of intercourse, in 88% it had been made within 20 years and in 100% it had been made by 30 years. These data suggest that a program based on number of years of intercourse may be more uniform and more efficient than one based on chronologic age, and that cytologic examinations should be concentrated during the time when most cases develop -- 6 to 20 years after the time of first intercourse.