The Cardiff cervical cytology study. Enumeration and definition of population and initial acceptance rates.

The Cardiff Cervical Cytology Study began in 1965. Its primary aim was to evaluate screening for neoplasia of the cervix uteri. The study population was all ever-married women, aged 25--69, resident within the Cardiff City area. The basic objective was that all such women should be screened three times. The population was enumerated by house-to-house visiting of the entire city and a register of eligible women was compiled. The first round of visiting finished early in 1971. The defined population numbered 70 869, of whom 45 915 (65%) had had one or more tests. The method of defining the population is described and details are given of the initial response rates in respect of the major demographic factors. The response rate varied with age and with social class. It declined from 92% in the age group 25--29 to 26% in the age group 65--69, and from 81% in Social Class I to 52% in Social Class V. The response was 5% to 10% lower among widowed, divorced, and separated women than among married women but was independent of age at first marriage and age at first pregnancy. Nulliparae showed a lower response rate than multiparae.