Abstract
Prospective studies are key study designs when attempting to unravel health mechanisms that are widely applicable. Understanding the internal validity of a prospective study is essential to judge a study’s quality. Moreover, insights in possible sampling bias and the external validity of a prospective study are useful to judge the applicability of a study’s findings. We evaluated participation, retention, and associated factors of women in a multicenter prospective cohort (FemCure) to understand the study’s validity.Chlamydia trachomatis (CT) infected adult women, negative for HIV, syphilis, and Neisseria gonorrhoeae were eligible to be preselected and included at three sexually transmitted infection (STI) clinics in the Netherlands (2016–2017). The planned follow-up for participants was 3 months, with two weekly rectal and vaginal CT self-sampling and online questionnaires administered at home and at the clinic. We calculated the proportions of preselected, included, and retained (completed follow-up) women. Associations with non-preselection, noninclusion, and non-retention (called attrition) were assessed (logistic and Cox regression).Among the 4,916 women, 1,763 (35.9%) were preselected, of whom 560 (31.8%) were included. The study population had diverse baseline characteristics: study site, migration background, high education, and no STI history were associated with non-preselection and noninclusion. Retention was 76.3% (n = 427). Attrition was 10.71/100 person/month (95% confidence interval 9.97, 12.69) and was associated with young age and low education. In an outpatient clinical setting, it proved feasible to include and retain women in an intensive prospective cohort. External validity was limited as the study population was not representative (sampling bias), but this did not affect the internal validity. Selective attrition, however (potential selection bias), should be accounted for when interpreting the study results.
Highlights
Prospective studies are key study designs for assessing the risks of certain determinants in acquiring a specific disease in an attempt to unravel health mechanisms that are widely applicable [1,2]
We demonstrated that chlamydia-infected women can be included and retained in an intensive prospective cohort with 3 months of follow-up
Communication: satisfied Study clinic visits: satisfied Overall experience with study: good Main reasons for participation Contribute to more knowledge on rectal chlamydia I could have rectal chlamydia even without anal sex To help others At the end of the study, to receive a chlamydia test with result and treatment Monetary incentive
Summary
Prospective studies are key study designs for assessing the risks of certain determinants in acquiring a specific disease in an attempt to unravel health mechanisms that are widely applicable [1,2]. Women’s participation in prospective studies is fundamental to understanding their health mechanisms [3]. First and foremost, a prospective study should have high internal validity to generate unconfounded insights [1]. Internal validity may be compromised when it is difficult to include sufficient participants. Similar threats to internal validity arise when insufficient participants are retained, i.e., when a large portion of included women is lost to follow-up or withdraws from the study (both called attrition). Education Low Middle High Unknown a STI history Yes No Unknown a Anatomic site CT diagnosed vCT (rCT not tested) vCT (rCT negative) vCT & rCT rCT (vCT negative)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call