Our study design was informed by the Health Equity Measurement Framework, which emphasizes the role of social stratification processes at the root of inequities and avoids inferring causal relationships as inherited by individuals [23]. Sociodemographic characteristics were used as markers of social location resulting from social stratification, which supported interpretations of GetCheckedOnline adoption in different groups.

We conducted a survey to evaluate awareness and use of GetCheckedOnline in communities where the service expanded with laboratory partners outside Vancouver to other urban, suburban, and rural communities in the province: Victoria, Langford, Kamloops, and Nelson in 2016, Kimberly in 2019, and Maple Ridge in 2020 (see map in Multimedia Appendix 1). The survey instrument included questions about GetCheckedOnline, participants’ experiences with STBBI testing, participants’ sexual health experiences, sociodemographic characteristics, and participants’ use of technology. The survey was piloted with 17 people from across BC, including 9 members of our community advisory board. We requested feedback on the questionnaire’s comprehension, readability, and flow and revised it accordingly.

Recruitment took place from July to September 2022 using in-person and online versions of the survey (to maximize recruitment of people with lower digital literacy or access to technology). Our inclusion criteria were residents of BC, 16 years of age or older, sexually active (defined as oral, vaginal, or anal sex with ≥1 partner in the past year), able to complete the survey in English, and not having completed the survey before. Public health and community organization STBBI leads were identified, and peer researchers were hired for each community. For in-person recruitment, these leads and peer researchers identified common gathering places and venues likely to include individuals facing barriers to accessing STBBI testing. These included 1-time and recurrent community events (eg, Pride festivals and markets) and fixed venues (eg, recreational center). At each venue, peer researchers approached potential participants, described the inclusion criteria, and obtained verbal informed consent with participants self-assessing their eligibility and self-administering the paper survey. Online recruitment occurred through community leaders and local agencies circulating study recruitment information by email, social media (eg, Facebook), and peer researchers putting up posters in venues with QR codes directing to the online survey. Additional recruitment occurred through geotargeted online advertising and promotion in online venues relevant to each community (eg, online forums). The online survey was administered through REDCap (Research Electronic Data Capture; Vanderbilt University) and included measures to prevent automated responses or bots (eg, requiring manual entry of a passphrase included in the survey). The survey was designed to take 10-15 minutes to complete. In-person completion times were not recorded. For the online survey, the median completion time was 12 (IQR 8-20) minutes.

The implementation outcomes for our study were self-reported awareness and use of GetCheckedOnline. Awareness was assessed with the question, “With GetCheckedOnline, you can get tested for sexually transmitted infections by printing a lab form or downloading an electronic version on your phone, that you then take to a lab, and then get your results online or by phone. Before today, did you know about GetCheckedOnline?” (responses: yes/no). Use was assessed by asking, “Have you been tested through GetCheckedOnline?” (responses: yes/no/not sure). The independent equity-relevant sociodemographic variables examined in relation to these outcomes were age, gender identity, sexual identity, race/ethnicity, educational attainment, and self-reported annual income. For annual income, a currency exchange rate of CAD $1=US $0.78 is applicable.

Paper surveys were entered into a database using a double-entry procedure by 2 independent researchers, with discrepancies resolved by a third independent researcher (question discrepancy rate ranged between 0% and 4.9%). In-person and online survey data were combined. Participants reporting age <16 years, 0 sexual partners in the past year, and living in locations outside BC were excluded. Online participants with missing or incorrect passphrases or discrepancies in start and completion times inconsistent with survey time zones were considered likely to be bots or ineligible participants and excluded.

We modeled awareness and use of GetCheckedOnline using logistic regression models to estimate the effect of each of our variables of interest. To build these models, we categorized numeric variables, built mutually exclusive categories for multiple-response survey questions, and selected reference groups. Under our hypothesis, those likely to experience the least barriers to digital STBBI testing services, such as GetCheckedOnline, were considered the most privileged group and served as the reference for comparisons. Age categories were based on sample quartiles (<25 years, 25-29 years [reference], 30‐37 years, and >38 years). While older age is typically associated with a privileged social location, we selected the 25‐29 years age group as the reference, as an age range favored by assumptions of digital health literacy (positioning younger people as “digital natives”) and targeting of technology marketing [24]. Gender was studied at 2 levels: the first (dimension 1: gender identity) included the categories of men only (reference), women only, and those identifying as genderfluid, genderqueer, agender, nonbinary, or selecting multiple gender identities (GGANB+); the second level (dimension 2: gender modality [25]) included cisgender (reference) and transgender categories. Sexual identity included those identifying as heterosexual only (reference) and lesbian, gay, bisexual, or other nonexclusively heterosexual identities (LGB+). Race/ethnicity included those identifying as White only (reference), Indigenous, and non-Indigenous racialized people (people of color). Additional details of the question to collect this data and how categories were built are included in Multimedia Appendix 1. Education (graduate degree; reference) and income (≥$80,000; reference) did not require further categorization.

Informed by the Health Equity Measurement Framework and the conceptualization of sociodemographic characteristics as proxy variables for multiple social stratification processes [23], we built the directed acyclic graph in Figure 1. We used the DAGitty software (Johannes Textor, Institute for Computing and Information Sciences, Radboud University) to identify the minimal sufficient adjustment set for each of our exposures of interest [26,27]. We built variable-specific models to obtain total direct effects for each exposure [28]. Missing responses were excluded from the analyses. Sensitivity analyses included the assessment of awareness and use distribution comparing those with complete vs missing sociodemographic information using the Fisher exact test to test for differences and identify the potential effects of their exclusion. We report estimated total direct effects through odds ratios (ORs) or adjusted odds ratios (aORs) with 95% CIs. All statistical analyses were conducted using R software (version 4.1.3; R Foundation for Statistical Computing) and its tidyverse package [29,30].

The informed consent procedure was carried out by peer researchers at each venue, who explained the study and obtained verbal consent before handing out surveys to participants. Online and in-person participants completing the survey could enter a draw for 1 of 5 CAD $100 (US $78) VISA gift cards by providing contact information that was not linked to their responses. Participants recruited in person were also offered GetCheckedOnline branded promotional materials. Paper survey responses were digitized by 2 core team members and kept with restricted access at the BC Centre for Disease Control. Compiled electronic data from paper and online surveys was stored in secure servers at the BC Centre for Disease Control Central Data Repository. The execution and analysis of the GetCheckedOnline community survey were examined and approved by the Behavioral Research Ethics Board of the University of British Columbia (Vancouver, BC, Canada) under the GetCheckedOnline Implementation Science Grant (ID H18-00437).

Awareness and use of GetCheckedOnline were high (approximately 1 in 3 and 1 in 5, respectively) in this sample of people in 5 communities where GetCheckedOnline is available. We found that differences in sociodemographic characteristics were associated with awareness and use of the service. Some of these differences favored more privileged groups (those in the central quartiles of age and those with higher income). In contrast, other differences favored equity-owed groups (people of color, transgender and gender-diverse participants, and nonheterosexual participants). Two groups—those identifying only as women and Indigenous people—showed similar or higher levels of awareness but not higher use of the service. This study makes an important contribution to the scant but growing literature on the equitable impacts of digital STBBI testing services by being one of the first to measure implementation outcomes across groups at a community level and to use a theoretically informed approach to health equity analyses. This approach has also allowed us to identify the specific equity-owed groups where further promotion of GetCheckedOnline may be needed to increase awareness, and where service adaptations may be required to increase use.

Our results align with other research evaluating health equity indicators of digital STBBI testing services, in which differential uptake patterns have been observed with complexity in the directions and magnitude of the effects [7]. Our findings related to age and income are consistent with an overall tendency of interventions favoring privileged groups [7]. However, our findings related to gender, sexual identity, and race/ethnicity follow a different direction, with at least some oppressed groups showing higher uptake. Other studies have reported differences favoring transgender and nonbinary individuals and nonheterosexual men [9,13,20], but all studies finding differences associated with race/ethnicity show higher uptake in White people [9,11,14].

The diffusion of innovations theory proposes concepts that can further support the interpretation of these differences, such as the concept of relative advantage and communication networks [31]. In this case, we examined the relative advantages of GetCheckedOnline over provider-based testing in the context of the social stratification processes generating differences in living conditions. Digital access might provide some individuals with an alternative to avoid contact with potential experiences of discrimination in the health care system [32,33], which is a known issue affecting sexual and gender minorities and people of color, even more so in areas away from larger urban centers [34]. Previous research on GetCheckedOnline has highlighted the benefits that gay, bisexual, and other men who have sex with men (GBMSM) describe in terms of privacy, control of sample collection, and access to testing by men who live outside of larger urban areas [32]. Transgender and gender-nonconforming individuals have also provided insights into their experiences testing, supporting GetCheckedOnline’s adaptation to offer a more inclusive service [35].

In addition, promotional efforts might also explain the higher awareness and use of GetCheckedOnline observed in some groups. Early promotion of GetCheckedOnline intentionally included representation of and directed marketing to GBMSM [36]. Historical targeting of HIV testing campaigns on GBMSM has also been related to a higher uptake of testing interventions by nonheterosexual men [11]. A higher perception of relative advantage and promotion efforts influences the diffusion through communication networks. This diffusion is more likely to occur among individuals who perceive themselves as similar [31], more so when topics related to sexual health and STBBI still carry a significant social stigma.

However, the service’s relative advantage is impacted by its requirement for digital devices and access to the internet, which has been shown to limit access to digital health services for those with lower incomes [5]. Similarly, GetCheckedOnline might be less appealing to those looking for additional services, such as human papillomavirus testing, vaccines, or contraception. In other digital STBBI testing programs, lower uptake in women has been associated with their access to testing in the context of other health-related visits [9]. In other cases, provider-based testing may appear as a more acceptable health care pathway, which might relate to older individuals’ trust in and preference for in-person services. In contrast, GetCheckedOnline, as a provincial service, might be perceived as part of the broader health care system, which in turn carries a sense of mistrust from Indigenous communities, coming from the historical and present harms that the colonial systems have perpetrated on them [37]. In addition, they might not see themselves reflected in the service promotion, as GetCheckedOnline has not been promoted directly to Indigenous people in the locations included in this study.

Our study had the following limitations. Digital STBBI testing services include diverse service models that might not share essential features of GetCheckedOnline (eg, relying on external laboratory partners); therefore, findings might not be generalizable to other digital STBBI testing interventions. Our approach allowed us to estimate the differences associated with the selected sociodemographic characteristics as markers of social location. However, these differences should not be interpreted as the only determinants of the outcomes of our study. Although previous research on GetCheckedOnline has shown that variables related to sexual history (eg, behaviors, relationship status, and prior STBBI diagnoses) were not as strongly associated with awareness and use as sociodemographic characteristics [22], these variables may still account for differences in the service implementation outcomes. Similarly, our findings describe the differences associated with markers of social location in these urban, suburban, and rural communities. However, given that geographic location and urbanity function both as materialization and reproduction of social stratification processes [23,38], further analyses and comparisons with larger urban areas may be needed to better understand the role of geographic location on these implementation outcomes.

Furthermore, we relied on self-reported data, which may be subject to volunteer or recall bias, particularly related to implementation outcomes, and some participants did not provide complete sociodemographic information. Sensitivity analyses showed that GetCheckedOnline use significantly differed only between those who provided complete sociodemographic information and those who did provide some or no sociodemographic details. However, given the size effect of our found associations and the size of this group, we believe that missing data exclusion would be unlikely to bias the direction of these associations.

Future research can support understanding this complex distribution of service uptake by sociodemographic characteristics. Critical to understanding these uptake patterns is exploring the interactions between different social stratification processes acting simultaneously through an intersectionality lens. Understanding these social processes and focusing on modifiable factors could inform program adjustments. Local context factors at the community level, such as the availability, acceptability, and appropriateness of testing services, play a significant role in service uptake. More research is needed to understand how social stratification processes affect these factors and inform service adaptation as a response. Longitudinal studies can show if the patterns we observed in this study are maintained over time and describe the dynamics of service penetration.

In conclusion, our study found that patterns of awareness and use of BC’s digital STBBI testing service were associated with sociodemographic characteristics that reflect social stratification processes. Our findings suggest that GetCheckedOnline seems to respond equitably to the needs of some equity-owed groups (eg, sexual and gender minorities and people of color). However, further understanding of the lower uptake in other equity-owed groups (eg, lower-income people) is needed. These findings support the need for continuous evaluation of digital STBBI testing programs, and developers should evaluate the factors affecting equity in their local context. Efforts to promote and adapt digital STBBI testing interventions must consider the existing uptake pattern and the social and material circumstances determining accessibility to the service to ensure services reach those who experience a higher burden of these infections.