The US burden of bacterial sexually transmitted infections (STIs) (syphilis, chlamydia, and gonorrhea) and human immunodeficiency virus (HIV) is concentrated in men who have sex with men (MSM). Although they make up 2% of the US population, MSM experienced 68.2% of the 30,644 cases of primary and secondary syphilis in 2017,1 2 3,4 5–7
STI partner services (PS) present an opportunity to link all individuals diagnosed with STIs—who are at elevated risk of subsequent infection—to prevention services, including regular testing for STIs and HIV.8 9 10–12 13,14 15–18 19 20,21 22
Since July 2013, PS in King County, Washington, have offered quarterly SMS reminders for HIV and STI testing to MSM diagnosed with early syphilis, gonorrhea, and/or chlamydia. This initiative was delivered as part of a broader effort to leverage STI PS for HIV prevention in Washington State, where greater than 70% of people living with HIV are MSM.23,24
MATERIALS AND METHODS
STI Case Reporting
Medical providers in Washington State are legally required to complete a case report for each person they diagnose with syphilis, gonorrhea, or chlamydia. Clinical laboratories are also required to report these infections, and public health staff follow-up on laboratory-reported cases to ensure case reports are complete. The case report includes gender of sex partners and anatomical site of gonococcal and chlamydial infection, allowing health departments to identify MSM.
Partner Services SMS Reminder Intervention
Since 2012, PS in King County, Washington, have attempted to reach all MSM with early syphilis and those with gonorrhea or chlamydia as resources allow. Resource allocation was based on available funding, with priority given to untreated individuals and those who could be linked with other services offered by the public health department. In July 2013, PS began offering quarterly SMS testing reminders to interviewed MSM, using an external vendor, 2SMS25
Study Population and Data Sources
This analysis used STI surveillance and PS data, matched to the Washington State Enhanced HIV/acquired immune deficiency syndrome Reporting System. The analysis was restricted to MSM, defined as individuals identified as cis or trans male gender in their case report form or PS interview, and who met any of the following criteria: (1) they reported sex with men in the prior year during PS interviews, (2) their provider indicated male sex partners on the case report, or (3) they were diagnosed with rectal gonorrhea or rectal chlamydia. The STI diagnoses between July 1, 2013, and January 17, 2018. All activities were part of public health program evaluation and therefore not considered human subjects research.
Statistical Analysis
We conducted analyses to determine (1) the level and correlates of SMS reminder use at and before PS interviews, and (2) the effect of SMS reminder use on HIV/STI testing frequency.
We identified correlates of SMS use before PS interview and correlates of SMS acceptance at PS interview using Poisson regression with robust standard errors. For clients with multiple PS interviews at which they were offered SMS reminders, only the first response was included in all analyses to standardize the exposure definition in all clients to 1 offer of SMS reminders. Thirty-two individuals who initially refused SMS reminders subsequently accepted them; these are counted as refused in this analysis. Univariable and multivariable analyses were conducted; all variables significantly associated with SMS use/acceptance in univariable analysis at a P value of 0.1 or less were included in the multivariable model.
We assessed the effect of SMS reminders on testing through two approaches: (1) association between SMS reminder use and testing frequency before PS interview, and (2) association between acceptance of SMS reminders at PS interview and subsequent testing.
We determined the association between SMS reminder use before PS interview and time from most recent HIV test to the current STI diagnosis using median regression. Time from last HIV test was used as a proxy for HIV and STI testing frequency and was determined based on client self-report in the PS interview.26,27 28 P value of 0.1 or less were included in the adjusted analysis.29
We determined the association between SMS reminder uptake at PS interview and subsequent diagnosis with an asymptomatic STI within 1 to 12 months after the initial STI diagnosis, using Poisson regression with robust standard errors. This analysis was restricted to asymptomatic STIs because symptoms would be expected to influence care seeking. This analysis was also restricted to initial diagnoses before January 17, 2017 (1 year before data freeze) to allow all cases equal opportunity to experience the outcome. Unadjusted and adjusted analyses were conducted; all variables identified as univariable correlates of SMS reminder uptake at PS interview at a P value of 0.1 or less were included in the adjusted analysis.
All analyses were conducted in Stata version 13 (College Station, TX). A P value cutoff of 0.05 was used to determine statistical significance.
RESULTS
Participant Characteristics
Between July 1, 2013, and January 17, 2018, medical providers and laboratories reported cases of bacterial STI in 8236 unique MSM in King County. Of these, public health staff interviewed 5237 (64%) MSM for PS, and offered 4087 (78%) of them SMS reminders. Proportions interviewed by PS were similar across race and age groups, but varied by STI and HIV status: 76% of syphilis cases were interviewed compared with 36% of chlamydia cases, and 98% of HIV-negative compared with 51% of HIV-positive cases. Table 1 summarizes the demographic characteristics of MSM offered SMS reminders. Most men were white (62%) or Hispanic/Latinx (18%) and younger than 35 years (62%). Four hundred sixty (11%) cases were diagnosed with early syphilis (with or without other STIs), 2380 (58%) with gonorrhea in the absence of early syphilis, and 1247 (31%) with chlamydia alone. Around a quarter of participants (24%) were known to be living with HIV, and 30% of HIV-uninfected men were using PrEP.
TABLE 1: Sociodemographic, Clinical, and Behavioral Characteristics of MSM Offered SMS Testing Reminders Through STI Partner Services in King County, WA, 2013–2017
Uptake and Prior Use of SMS Reminders
Among 4087 MSM offered SMS testing reminders during PS interviews, 545 (13%) accepted (Fig. 1 ). Two hundred sixty-five men (7%) were already receiving SMS reminders for HIV/STI testing through enrollment outside of PS (from community organizations or websites), and the remaining 3277 (80%) refused. Of those who refused, 2602 were asked what, if any, non-SMS reminder systems they were using to prompt them to test for HIV/STI. Approximately a quarter (679, 26%) used reminders, such as smartphone apps, calendar reminders, notes to self, or other unspecified methods; 531 (20%) tested as part of HIV well-care visits or routine physical examinations; 425 (16%) were reminded to test by health care providers outside of Public Health-Seattle & King County; 967 (37%) had no reminder in place.
Figure 1: Uptake of SMS reminders and other reminder use among MSM interviewed by partner services in King County, WA, 2013 to 2017.
Table 2 summarizes the characteristics associated with already using SMS reminders at the time of initial PS interview through enrollment from another source. In univariable analysis, already using SMS reminders was associated with younger age (9% of men ≤24 years old accepted SMS reminders vs. 3% of men ≥45 years old), diagnosis by an HIV/STI specialist provider (defined as an STI clinic, HIV/STI testing program, or medical provider specializing in HIV or STI care or MSM health; 9% uptake among those diagnosed by a specialist vs. 2% diagnosed by nonspecialist), and not having health insurance (11% uptake among uninsured vs. 6% among insured). Prior SMS reminder use was associated with type of STI diagnosis: it was highest among men diagnosed with chlamydia only (8% uptake), followed by those diagnosed with gonorrhea (7%), and significantly lower among men diagnosed with syphilis (1%). Reminder use was also associated with HIV status: it was significantly higher among HIV-negative men not using PrEP (8%) than HIV-positive men (1%). There was also a secular decline in SMS reminder use over calendar time (relative risk (RR), 0.81 [0.73–0.89] per calendar year increase). In multivariable regression, use of SMS reminders before PS interview was associated with younger age, nonsyphilis STI diagnosis, negative HIV status, diagnosis by an HIV/STI specialist, and earlier calendar year of diagnosis.
TABLE 2: Correlates of Receiving SMS Testing Reminders Before STI Partner Services Interview among all MSM Offered SMS Reminders in King County, WA, 2013–2017
Table 3 summarizes sociodemographic, behavioral, and clinical characteristics associated with uptake of SMS testing reminders offered at PS interview among men who were not already receiving SMS before PS interview. Characteristics associated with SMS reminder uptake at PS interview were similar to those associated with use before PS interview. In univariable analyses, uptake of SMS reminders was associated with younger age (23% of men ≤24 years old accepted SMS reminders vs. 9% of men ≥45 years old) and nonwhite race/ethnicity (12% uptake by white men vs. 18% uptake by men of color). Reminder uptake was highest among men diagnosed with chlamydia only (19% uptake) than those with gonorrhea (14%) or syphilis (2%). It was also associated with diagnosis by an STI specialist provider (15% uptake among those diagnosed by a specialist vs. 13%), with not having health insurance (23% uptake among uninsured vs. 12%), and with HIV status and PrEP usage (13% uptake among HIV-negative men not using PrEP, 3% among HIV-negative men using PrEP, and 7% among HIV-positive men). There was also a secular decline in SMS uptake over calendar time (RR, 0.56 [0.52–0.60] per calendar year increase). In multivariable regression, SMS reminder uptake remained associated with younger age, STI diagnosis, HIV-negative status not using PrEP, and earlier calendar year of diagnosis (P < 0.05 for all).
TABLE 3: Correlates of SMS Testing Reminder Uptake at STI Partner Services Interview Among MSM Not Already Receiving SMS Reminders in King County, WA, 2013–2017
Association Between SMS Reminder Use and HIV/STI Testing Before PS Interview
We evaluated the association between SMS use before PS interview and time from last negative HIV test to the current STI diagnosis, among HIV-uninfected men diagnosed with an asymptomatic STI. Among 1457 men included in this analysis, 167 (12%) were using SMS reminders, 52 (4%) were tested as part of routine physicals, 724 (50%) used other non-SMS reminder systems, and 514 (35%) had no reminder system in place. Table 4 summarizes the median time since last HIV test by testing reminder. Overall, the median time since last HIV test was 4.1 months (IQR 2.9–7.7). Median time since last HIV test was shortest in men using non-SMS reminders, such as apps, calendar reminders, or reminders from providers outside Public Health-Seattle and King County (3.6 months [2.6–5.7]), followed by those using SMS reminders (4.7 months [3.1–7.7]), no reminder (5.6 months [3.3–10.7]), and physicals (9.6 months [4.0–17.5]). In multivariable analysis adjusted for client characteristics associated with SMS uptake before PS (age, PrEP use, STI, health insurance status, diagnosing provider and calendar year) men using physicals as their reminder had a significantly longer time since last HIV test, compared with men using SMS reminders (β, 4.33 [2.86 to 5.81]). There was a nonsignificant trend for longer time since last test in men using no reminder compared with those using SMS reminders (β = 0.80 [−0.08 to 1.68]).
TABLE 4: Association between Reminder Use Before STI Partner Services Interview and Time from Last HIV Test to Asymptomatic STI Diagnosis among HIV-negative MSM in King County, WA, 2014–2017
Association Between SMS Reminder Uptake and Asymptomatic STI Diagnosis After PS Interview
The second measure of association between SMS reminder uptake and testing frequency was repeat diagnosis with an asymptomatic STI 1 to 12 months after initial STI diagnosis. Of 3376 men who were offered SMS reminders and included in this analysis, 759 (23%) had a subsequent asymptomatic STI diagnosis within 1 to 12 months (Table 5 ). The frequency of subsequent diagnosis with an asymptomatic STI was not significantly associated with SMS reminder uptake at PS interview (19% subsequently diagnosed) or having been enrolled in SMS reminders before PS (25% subsequently diagnosed, P > 0.05 for both). Multivariable regression adjusted for variables associated with uptake of SMS reminders (age, race, HIV/PrEP status, STI, health insurance status, diagnosing provider, and calendar year) did not alter the effect estimates.
TABLE 5: Association Between SMS Testing Reminder Uptake at Partner Services Interview and Diagnosis With an Asymptomatic STI Within 1–12 Months after Initial Diagnosis in MSM in King County, WA, 2013–2017
DISCUSSION
In this analysis of public health programmatic data, we found that offering SMS testing reminders to MSM diagnosed with STIs through PS interviews was feasible, with 80% of clients interviewed between 2013 and 2018 being offered the service. However, SMS reminder uptake was low (13%) and declined over the period of analysis. Most MSM who refused SMS reminders cited having other reminder systems in place. SMS reminder uptake at PS interview was highest in younger MSM, those diagnosed with chlamydia only, and HIV-negative MSM who were not using PrEP. We found that HIV-negative MSM who used SMS reminders before PS interview had a shorter time since last HIV test (used as a proxy for STI testing frequency) compared with those using annual physical examinations as a reminder, and a trend for shorter time compared with those using no reminders. However, postinterview diagnosis with an asymptomatic STI was not associated with SMS reminder use either before or as a result of PS interview.
SMS messaging has been identified as a promising intervention to promote regular HIV/STI testing based on 3 main premises. First, SMS messaging is considered a relatively feasible, affordable intervention that places lower burden on the health system than in-person testing promotion or phone calls. Second, use of mobile technology, which now has almost universal penetration in the US,9 30 10–12 13,14 15–21
Our findings speak to each of these premises. Consistent with prior studies,15–18,22 1 after the decision to use SMS reminders, current STI diagnosis is known to be associated with prior diagnosis and risk behavior.31
Our analyses of the impact of SMS reminder use on testing frequency yielded two differing results. Analysis of SMS reminder use and HIV testing before PS interview indicated that SMS reminders were associated with more frequent testing than only testing concurrent with physical examinations. There was also a trend for more frequent testing in SMS users than those with no reminders, but no difference with users of other non-SMS reminders. This suggests that MSM who state they are using annual physical examinations as their reminder or have no testing reminder in place may benefit from targeted promotion of SMS reminders, and messaging that annual physicals do not constitute an adequate reminder system for at-risk MSM. The observational design of this study limited our ability to infer causality; however, our observation of shorter intertest interval when adjusting for client characteristics associated with SMS reminder uptake supports prior studies, suggesting that SMS reminders lead to more frequent testing.15,17–21 after it. This analysis was limited by our inability to ascertain testing directly using available data sources; instead, we relied on STI diagnosis data. It is therefore possible that testing frequency was higher among MSM who accepted SMS reminders, but that the underlying STI acquisition risk was lower in this group, impairing our ability to detect the association when evaluating STI diagnoses. Similarly, although a multivariable analysis was conducted adjusting for factors associated with SMS reminder uptake, it is possible that our estimate was residually confounded by other participant characteristics. Additionally, it is important to note that overall testing frequency in this population was high: median time since last HIV test was 4.1 months. This may have limited our statistical power to detect a difference in testing frequency between groups. Evaluation of this approach in contexts with lower baseline testing rates, with prospective ascertainment of testing events, and in a randomized design would be valuable.
The mechanism by which SMS messaging modifies human behavior is unclear. In the context of medication adherence, increasing access to information and building trust and two-way communication between patients and providers are thought to be important.10 15–17,20 19,21 17 32 33
In conclusion, this work adds to the literature supporting the use of SMS messaging to promote HIV/STI testing. The intervention was feasibly delivered as part of an expanded PS program,8 34
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