Characterizing participants who respond to text, email, phone calls, or postcards in a SARS-CoV-2 prevalence study

Abstract Introduction: Multiple modalities and frequencies of contact are needed to maximize recruitment in many public health surveys. The purpose of the current analysis is to characterize respondents to a statewide SARS-CoV-2 testing study whose participation followed either the postcard, phone outreach or electronic means of invitation. In addition, we examine how participant characteristics differ based upon the number of contacts needed to elicit participation. Methods Study participants were randomly selected to represent Indiana residents and were invited to participated via postcard, text/emails, and/or robocalls/texts based upon available contact information. The modality and frequency of contacts that prompted participation was determined by when the notification was sent and when the participant registered for the study. Chi square analyses were used to determine difference between groups and significant findings were analyzed using multinomial logistic regression. Results Respondents included 3,658 individuals and were stratified by postcards (7.9%), text/emails (26.5%), and robocalls/text (65.7%) with 19.7% registering after 1 contact, 47.9% after 2 contacts, and 32.4% after 3 contacts encouraging participation. Females made up 54.6% of the sample and responded at a higher rate for postcards (8.2% vs. 7.5%) and text/emails (28.1 vs. 24.6%) as compared to males (χ 2 = 7.43, p = 0.025). Compared to males, females responded at a higher percentage after 1 contact (21.4 vs. 17.9%, χ 2 = 7.6, p = 0.023). With respect to age, those over 60 years respondent least often following 1 contact and most often after 2 contacts (χ 2 = 27.5, p < 0.001). The regression model reinforced that participant sex (p = 0.036) age (p = 0.005), educational attainment (p = < 0.0001) were predictors of participation along with free testing (p = 0.036). Discussion Researchers should be aware that the modality of contact as well as the number of prompts used could influence differential participation in public health surveys by different demographic groups. Our findings can inform researchers wanting to increase participation from targeted demographic groups by using certain modalities and frequencies of contact in any study that relies on selective participation by study subjects.