Optimization of compliance in epidemiologic research and disease prevention : With special emphasis on PAP-smear screening

Sammanfattning: The aim of this thesis was to investigate factors affecting attendance in screening for cervical cancer, and to evaluate various measures aimed at increasing compliance to self-administered postal questionnaires and screening for cervical cancer. A population-based randomized controlled trial including 2000 men and women aged 20-79 years and living in Sweden was conducted to investigate compliance to postal questionnaires. In a randomized 2 3 factorial design three factors were tested: 1) preliminary notification or not, 2), questionnaire length, and 3) mention of a possible telephone contact or not. Preliminary notification increased the response rate by 7%, a short questionnaire with 5%, whereas mention of a possible telephone contact did not influence attendance. Combinations of preliminary notification and short questionnaires increased the response rate by 16%, whereas young age, male gender and urban residence lowered the response rate. The relation between non-attendance to screening for cervical cancer (Pap smear screening) and sociodemographic factors, gynecological examinations, risk behavior, general health behavior, knowledge, attitudes and beliefs was investigated in a population-based case-control study with 430 non-attenders and 514 attenders at Pap smear screening in Uppsala county. Non-attendance was more likely among women who had not used oral contraceptives, who had not taken their own initiative to a Pap smear, who had visited different gynecologists, and who had visited a physician very often or not at all. Regular condom use, living in rural/semirural areas, and not knowing the recommended screening interval were all associated with non-attendance, whereas socioeconomic status was not, when tested in a multivariate model. Multivariate analysis also showed that non-attendance was more likely among women who did not perceive cervical cancer to be as severe as other malignancies, who did not perceive the benefits of a Pap smear, who had time-consuming and economical barriers, and who did not feel anxious about the test results or cervical cancer. The results were strengthened with increasing time since the last smear or if self-reported attendance status was used instead of true attendance. Non-attenders also kept holding on harder to their preferences than did attenders, stating that they would not participate if their preferences were not met and were less likely to intend to participate in future screening. Among the non-attenders, 57% underestimated the time lapse since the last smear. Modifications of the invitation and call-recall system for Pap smear screening was investigated in a randomized controlled trial including all 12,240 women invited to organized screening during 17 weeks in 2001 in Uppsala County. Three successive interventions were tested: 1) modified invitation vs. the standard invitation letter, 2) reminder letter vs. no reminder letter, and 3) phone reminder vs. no phone reminder. Whereas the modified invitation did not increase attendance, a reminder letter increased the proportion attending by 9%, and a phone reminder by 31%. Combinations of modified invitation, written reminder and phone reminder almost doubled attendance within 12 months, and the number of detected cytologic abnormalities was more than tripled. Keywords: Compliance; epidemiological studies, self-administrated postal questionnaires, response rate; Pap smear screening, cervical cancer; non-attendance, socioeconomic factors, gynecological history, attitudes, beliefs, knowledge; manipulations, information, reminders; randomized controlled trial; case-control study.