Effect on attendance by including focused information on spirometry in preventive health checks: study protocol for a randomized controlled trial

Background: Early detection of lung diseases can help to reduce their severity. Lung diseases are among the most frequently occurring and serious diseases worldwide; nonetheless, many patients remain undiagnosed. Preventive health checks including spirometry can detect lung diseases at early stages; however, recruitment for health checks remains a challenge, and little is known about what motivates the attendance. The aim of the study is to examine whether focused information on spirometry in the invitation compared to general information will impact the attendance rate in preventive health checks. Methods/design: This randomized, controlled trial tests the effect of information on spirometry embedded in the Check your Health Preventive Program (CHPP). The CHPP is an open-label, household cluster-randomized, controlled trial offering a preventive health check to 30- to -49-year-olds in a Danish municipality from 2012 to 2017 (n = 26,216). During 2015-2016, 4356 citizens aged 30-49 years will be randomized into two groups. The intervention group receives an invitation which highlights the value and contents of spirometry as part of a health check and information about lung diseases. The comparison group receives a standard invitation containing practical information and specifies the contents of the general health check. Outcomes are (1) differences in attendance rates measured by the proportion of citizens attending each of the two study groups and (2) proportion of persons at risk defined by smoking status and self-reported lung symptoms in the study groups. The proportion of participants with abnormal spirometry assessed at the preventive health check will be compared between the two study groups. Discussion: The results from the present study will inform future recruitment strategies to health checks. The developed material on content, value, and information about lung disease is feasible and transferable to other populations, making it easy to implement if effective.