Navigating online recruitment for health research: A case study

The objective was to recruit 800 participants for a research study examining online health information exposure and engagement. Removing duplicate and/or fraudulent responses emerged as a major challenge during data collection.

Most recruitment took place online through U.S. national volunteer registries. Participants were required to share Facebook timeline data and take an online survey. We describe initial indicators of fraud and our process to create a prevention and exclusion protocol. We added three automatic prevention methods: CAPTCHA, blocking users with Virtual Private Network (VPN) and non-U.S. IP addresses, and requiring at least three years of Facebook timeline history. Additionally, we manually reviewed all responses, checking payment information, demographics, and IP addresses.

During the two months that the VPN/IP block was live, 7% of entries were blocked for using a VPN or having an IP address outside the U.S. 7% of consented participants who shared Facebook data were automatically excluded based on having insufficient timeline post history. Two months after implementing the VPN check, fraudulent enrollments stopped. Ultimately, 9.6% of enrollments were excluded based on suspected fraud.

Other than the Facebook post history check the VPN/IP block had the largest impact on preventing misrepresentative and/or fraudulent entries. We share three strategies for online recruitment: create and test a protocol for preventing and excluding fraud before data collection starts; review participants before payment; and add a VPN block to the beginning of your survey.