The Danish Symptom Cohort: Questionnaire and Feasibility in the Nationwide Study on Symptom Experience and Healthcare-Seeking among 100 000 Individuals

. In order to develop strategies to prevent delay in diagnosis, it is important to gain knowledge of symptoms and healthcare-seeking processes in the population. This paper describes a combined survey and register-based study with (1) focus on development of a questionnaire concerning experience of symptoms and subsequent consequences and (2) feasibility of the study. Methods . The study is a nationwide cohort study of 100 000 individuals randomly selected from the Danish general population. A comprehensive questionnaire concerning experience of symptoms and subsequent consequences was developed. The methodological framework for the development included defining the domains to be measured, identification of previous items, scales and questionnaires in the literature, and pilot and field testing. Results . A total of five domains and 16 subdomains were defined covering the area of symptom experience, symptom characteristics, reaction in response to symptom experience, external factors, and personality characteristics with potential influence on the symptom experience. In total, 49 706 questionnaires were completed, yielding a response rate of 52.2%. Conclusion . We developed a comprehensive questionnaire used in a large combined survey and register-based study concerning experience of symptoms and subsequent consequences of symptom experiences. We succeeded in conducting a large survey providing the groundwork for The Danish Symptom Cohort.