Conducting randomized controlled trials (RCTs) using digital technologies is potentially an accessible, low cost and strategic approach to investigate interventions to improve the beliefs of consumers with regard to low back pain (LBP). However, there are challenges with this research approach, considering that Brazil is a large populous country, and restricted funding scenarios present difficulties for recruitment and follow-up in digital RCTs.

To describe the recruitment process and recruitment rates, as well as follow-up rates during an RCT using digital recruitment and follow-up strategies.

This observational study is secondary to the RCT registered in The Brazilian Registry of Clinical Trials (RBR-10kpgx78). We invited Brazilian residents to tell us what they think about LBP and recorded their responses in Research Electronic Data Capture (REDCap). Until March 15th, 2023, we used three digital recruitment strategies: 1) posts on social networks; 2) paid traffic; 3) WhatsAppⓇ messages. We collected outcomes at immediate and eight-week follow-up after exposure to health education materials. The immediate follow-up must be answered soon after the exposure, otherwise, we send return reminders by: 1) e-mail integrated into REDCap; 2) WhatsAppⓇ; 3) social networks; 4) e-mail of the responsible researcher; daily for the immediate follow-up and every three days for the eight-week follow-up. In this study, we describe the strategies and recruitment rate (randomized people in relation to those who started the survey); response rates (proportion of those who responded to the follow-up in relation to those randomized eligible for that stage).

Recruitment started on December 16th, 2022, and we considered data from 170 adult participants. We posted 32 publications on social media profiles. We invested R$142,35 in two 7-day paid traffic campaigns, reaching 26,203 accounts, click-through rate of 2.19% and conversion rate of 2.78%. We sent WhatsAppⓇ messages in bulk on two specific days: 1) 19/12/22, with 60 new recruits in one week; 2) 31/01/23, with 65 new recruits at the same time. In three months, we have 205 respondents to the invitation and 170 randomized, indicating a recruitment rate of 82.9%. The response rates for the immediate and eight-week follow-up are 81.2% and 28.3%, respectively, and the median response times are 6.1 and 64.9 days, in that order. Immediate follow-up was completed right away by 39.9% of the participants and the return via WhatsAppⓇ reminders represented 46.4%. At the eight-week follow-up, e-mails integrated into REDCap accounted for 57.7% of survey returns.

The rates show the viability of combined recruitment strategies on social networks and WhatsAppⓇ. The retention of respondents during the RCT can be maintained through WhatsAppⓇ messages and e-mails integrated into REDCap.

Designing an electronically conducted RCT needs a diversified strategic plan for recruiting and retaining participants, as well as iterative monitoring of the results, in order to optimize recruitment and follow-up rates.