Behavioral characteristics and their association with syphilis seroprevalence among a cohort of young Black men who have sex with men

Abstract

The objective of this study was to describe the sociodemographic characteristics and behavioral factors that are associated with syphilis seroprevalence in a cohort of young Black men who have sex with men (YBMSM) in Chicago, USA (n = 606). The weighted syphilis seroprevalence in the study population was 29.2% (95% CI 23.9, 35.1). A bivariate probit multiple regression model was used to estimate the outcomes. Characteristics that were positively associated with syphilis seropositivity included being age 19–20, 21–24, and at least age 25 compared to the reference group (age 16–18 years old) (0.72 [95% CI 0.18, 1.25], 1.40 [95% CI 0.68, 2.13], and 1.34 [95% CI 0.75,1.94], respectively), using social media to meet sexual partners (0.33 [95% CI 0.05, 0.61]), using condoms more often (0.39 [95% CI 0.02, 0.76]), and a history of criminal justice involvement (0.25 [95% CI 0.06, 0.44]). Our study results suggest that among YBMSM in Chicago, interventions promoting condom use may be less effective for syphilis prevention compared to HIV prevention in this population. The contribution of nonpenetrative sex to syphilis prevalence requires additional research as does how best to implement routine syphilis screening and treatment for YBMSM in the context of ongoing syphilis transmission.

Keywords

Young Black men who have sex with men syphilis seroprevalence HIV infection health disparities transgender women sexually transmitted infections

Introduction

In the past 15 years, the rate of syphilis in the United States has more than tripled. Men who have sex with men (MSM) have been disproportionately affected by this increase. In 2016, 80.6% of male primary and secondary (P&S) syphilis cases with information on the sex of the sex partner occurred among MSM.¹ Among MSM, those who self-identify as Black or Latino have higher rates of P&S syphilis compared to non-Latino white MSM,^2,3 and young MSM (less than 30 years of age) have experienced the largest absolute increase in rates of P&S syphilis since 2005.² Moreover, HIV infection has been implicated as an important cofactor in syphilis among MSM, particularly among non-Latino Black and younger males (13–19 years of age).⁴

Some have attributed the increase in syphilis rates among young Black MSM (YBMSM) to HIV pre-exposure prophylaxis (PrEP).⁵ PrEP use, however, cannot fully explain the increase in syphilis in this demographic group, given the low numbers of YBMSM on PrEP and the even lower numbers who are retained in PrEP care.⁶ The current analysis, which includes a population-based cohort of YBMSM in Chicago between ages 16 and 29 years old at the time of enrollment, aims to examine the sociodemographic characteristics and behavioral factors that are associated with syphilis seropositivity in this at-risk population within a major urban HIV and syphilis epicenter in the United States.

Materials and methods

Study population

uConnect is a population-based cohort study of YBMSM in Chicago that examines how sociodemographic, health, behavioral, and social factors drive HIV prevention including PrEP, which was approved by the U.S. Food and Drug Administration in 2012. A sample of 618 respondents from a population of eligible YBMSM estimated to be approximately 5500 was recruited between June 2013 and July 2014.⁷ There were 12 subjects without either HIV or syphilis status available; therefore, 606 subjects were included in the final analysis. Study participants were eligible for inclusion if they (1) self-identified as African American or Black, (2) were assigned male sex at birth, (3) were between 16 and 29 years of age at the time of the initial interview, (4) spent the majority of their time on the South Side of the city, and (5) reported oral or anal sex with a male within the past 24 months.

Sample generation

Respondent-driven sampling (RDS) was used to generate the sample and estimate its statistical properties. The RDS methodology in the uConnect study has been described previously.⁷ Briefly, a panel of community partners nominated a diverse group of YBMSM in Chicago to serve as seeds. The seeds were identified via a broad range of sources (e.g. HIV clinics, community-based organizations, fraternities, House/Ball community, Facebook, or other websites), to ensure that the diversity of YBMSM was represented within the sample. Sixty-two seeds were recruited, of which 37 successfully recruited at least one additional individual to generate the total population of 618 respondents. Referral chains had a median length of 3 and a maximum length of 13. Productive seed analysis revealed no differences in HIV status, viral suppression, economic hardship, sexual orientation, criminal justice involvement, the use of hook-up apps, number of sex partners, and age at baseline between productive seeds and unproductive seeds.⁷

Data collection

All interviews were conducted using computer-aided personal interviewing. The interview itself included a wide spectrum of items: background and sociodemographic, behavioral, and clinical data that have been described in further detail in previous work with this population.⁸ Demographic data included age, race/ethnicity, self-reported HIV status, self-reported history of prior syphilis infection, and history of incarceration. Behavioral data included drug use, means of meeting potential sexual partners, as well as population-specific variables such as closeness to the Black community and gay community as well as membership in House/Ball community or gay family social structures. Among study participants who were either HIV-negative or did not know their HIV status, we asked whether or not they used condoms as a means of reducing their risk of contracting HIV. Among study participants who were HIV-positive, we asked whether or not they used condoms as a means of reducing their risk of transmitting HIV. Study participant’s self-reported degree of closeness to the gay community was assessed using an ordinal scale to answer the question: ‘How close do you feel to the gay community?’ with the option to select one of the following answers: ‘Very close; Somewhat close; Not very close; Not close at all.’ Exchange sex was defined as receiving drugs, money, shelter, or other goods in the past six months in exchange for sex. Using social media to meet potential sexual partners was defined as having used websites or mobile phone applications to meet or socialize with other men in the past 12 months. Frequency of marijuana use during sex was assessed using an ordinal scale to answer the question: ‘How often do you use marijuana when you have sex?’ with the option to select one of the following answers: ‘Always; Usually; Sometimes; Rarely; Never.’ Sex with a transgender woman was determined with the question: ‘Have you ever had oral, anal, or vaginal sex with a transgender woman?’ Participants’ awareness and usage of PrEP was determined by asking if they had ever heard of or ever used PrEP, respectively. Clinical data from Wave 1 of the uConnect cohort included HIV and syphilis testing, which was performed following survey administration. HIV infection status (including acute infection) was determined by fourth generation HIV immunoassay (Abbott ARCHITECT HIV Antigen/Antibody Combo assay, Abbott Laboratories, Abbott Park, IL), HIV-1/-2 Antibody differentiation (Bio-Rad Multispot HIV-1/-2 Rapid Test, Bio-Rad Laboratories Inc., Redmond, WA), and viral load testing (Abbott RealTime HIV-1 assay, Abbott Laboratories, Abbott Park, IL) applied to samples eluted from dry blood spots.⁹ Syphilis seropositivity was determined by Treponemal antibody testing (Bio-Plex Syphilis, Bio-Rad Laboratories Inc., Redmond, WA). A positive Treponemal antibody test may indicate either active syphilis, prior treated, or untreated syphilis. The institutional review board at the University of Chicago approved procedures and protocols. Informed consent was obtained from all respondents.

Statistical analyses

Descriptive analyses were conducted by using frequencies of sociodemographic characteristics, behavior, health, and social factors. Population-based estimates for syphilis seropositivity and HIV infection in the study sample were calculated using the weighted proportion of syphilis seropositivity and HIV seropositivity in the study sample.

In order to identify the sociodemographic characteristics and behavioral factors associated with both syphilis and HIV seroprevalence, a bivariate probit regression model was used to estimate the outcomes simultaneously and to correct a potential relationship between the outcomes. Variables with P values less than 0.20 in univariate analyses were selected to employ the bivariate probit multiple regression model. All moderate correlation coefficients (rho) of bivariate probit regression models between the bivariate outcomes were greater than 0.5, suggesting that the bivariate probit regression models were performed appropriately in this study. A two-tailed P-value less than 0.05 was considered to indicate statistical significance. All statistical tests were performed using STATA/SE software, version 14 (StataCorp LP, College Station, Texas, USA).

Results

Sample characteristics

Six hundred and six participants were included in the analysis. As indicated in Table 1, over 60% of the sample was between 19 and 24 years old (range 16–29 years old). Over 90% of participants had at least a high school degree. In addition, over 90% of YBMSM in our study identified as gay or bisexual. One-fourth experienced housing instability in the previous 12 months. A quarter had been tested for at least one anorectal sexual transmitted infection (STI) in the past 12 months. Thirty-seven percent were found to be HIV seropositive at the time of initial interview and laboratory data collection. Almost half (47%) of participants reported that they had been detained, arrested, or spent time in jail or prison.

Table 1.

Selected sample characteristics (N = 618), uConnect Study, Chicago.

Characteristic	N (%)^a,b
Age (years)
16–18	51 (8%)
19–20	117 (19%)
21–24	277 (45%)
25–29	173 (28%)
Education
Grade 0–12	39 (6%)
High school graduate/GED	201 (33%)
Completed some college	211 (34%)
Associate’s degree or technical/ vocational degree	126 (21%)
Bachelor’s degree/Master’s degree	40 (7%)
Not available	1 (0%)
Sexual orientation
Gay	410 (66%)
Straight	22 (4%)
Bisexual	167 (27%)
Other	18 (3%)
Unstably housed (past 12 months)	155 (25%)
Income ($)
<5000	267 (43%)
5000–9999	96 (16%)
10,000–14,999	81 (13%)
15,000–19,999	47 (8%)
20,000–24,999	56 (9%)
25,000+	53 (9%)
Criminal justice involvement (ever)^c	285 (46%)
Has had an anorectal STI test in the past 24 months	156 (25%)
HIV infection^d	176 (37%)^e
Syphilis seropositive^f	143 (32%)^g

^aMay not sum to 100% due to rounding.

^bThere was a total of 618 subjects in the uConnect wave 1 data. We used a bivariate profit regression model for both HIV and syphilis. If one of the HIV and syphilis results was missing, this subject was excluded from the model. There were 12 subjects without either HIV or syphilis status; therefore, we included 606 subjects in the final analysis for this study.

^cSubject has been detained, arrested, or spent time in jail or prison.

^dHIV infection status (including acute infection) was determined by fourth generation HIV immunoassay (Abbott ARCHITECT HIV Antigen/Antibody Combo assay), HIV-1/-2 Antibody differentiation (Bio-Rad Multispot HIV-1/-2 Rapid Test) and viral load testing (Abbott RealTime HIV-1 assay) applied to samples eluted from dry blood spots.

^eFour hundred and seventy-eight out of 618 subjects received HIV antibody testing.

^fSyphilis infection was determined by Treponemal antibody testing (Bio-Plex Syphilis).

^gFour hundred and forty-two out of 618 subjects received Treponema pallidum antibody testing.

Population-based proportion estimates of syphilis and HIV

As shown in Table 2, across all age ranges in the sample, syphilis seroprevalence was higher in the HIV-positive cohort than the HIV-negative cohort. The weighted total of syphilis seropositivity in the overall study population is estimated to be 29.2% (95% CI 23.9, 35.1). The ‘25–29 years of age’ group had the largest proportion of syphilis seropositivity 37.7% (95% CI 27.3, 49.4) in our study. Among those in the cohort who are HIV-positive, the weighted total of syphilis seropositivity was 54.1% (44.3, 63.6). The weighted seroprevalence was highest among those age 21–24 years old at 60.9% (50.3, 70.6), followed by those age 25–29 at 52.6% (34.7, 69.9). Nationwide, although Black MSM were only slightly more likely to be screened for syphilis, Black MSM had a substantially higher rate of P&S syphilis diagnosis (14%) than white MSM (8%) or Latino MSM (11%) men in 2014.¹⁰

Table 2.

Population-based proportion estimates of syphilis and HIV (N = 606), uConnect Study, Chicago.

Syphilis
	Age: 16–18 years		Age: 19–20 years		Age: 21–24 years		Age: 25–29 years		Overall
	SyphilisN (%)	Weighted syphilis% (95% CI)	SyphilisN (%)	Weighted syphilis% (95% CI)	SyphilisN (%)	Weighted syphilis% (95% CI)	SyphilisN (%)	Weighted syphilis% (95% CI)	SyphilisN (%)	Weighted syphilis% (95% CI)
HIV+	2(33.3)	22.8(3.3, 71.9)	8(33.3)	43.2(24.8, 63.7)	62(62.6)	60.9(50.3, 70.6)	51(60.7)	52.6(34.7, 69.9)	123(57.8)	54.1(44.3, 63.6)
HIV−	2(4.7)	1.8(0.4, 7.7)	12(13.0)	8.4(4.6, 14.7)	43(25.2)	24.1(16.4, 34.0)	23(26.4)	22.8(14.8, 33.5)	80(20.4)	17.1(14.2, 20.5)
Total	4(8.2)	4.1(1.1, 13.9)	20(17.2)	14.4(9.5, 21.2)	105(38.9)	36.2(28.8, 44.2)	74(43.3)	37.7(27.3, 49.4)	203(33.5)	29.2(23.9, 35.1)

Factors associated with syphilis seroprevalence and HIV infection

Bivariate probit regression analysis results that explored the relationship between various factors and syphilis and HIV seroprevalence are shown in Table 3. Some behaviors were found to have a significantly positive correlation with syphilis seropositivity but not HIV infection in the multivariate model. Being age 19–20, 21–24, and at least age 25 years were all significantly associated with syphilis seropositivity (0.72 [95% CI 0.18, 1.25], 1.40 [95% CI 0.68, 2.13], and 1.34 [95% CI 0.75, 1.94], respectively) compared to the reference group (age 16–18 years old) but had no significant association with HIV seropositivity (0.44 [95% CI −1.44, 0.55], 0.14 [95% CI −0.91,1.19], and 0.37 [95% CI −0.47, 1.20], respectively). Using condoms more often with the intention of reducing one's risk of contracting HIV was positively associated with syphilis seropositivity (0.39 [95% CI 0.02, 0.76]) but had no significant association with HIV seropositivity (0.22 [95% CI −0.19, 0.63]). Using social media to meet sexual partners in the past 12 months was positively associated with syphilis seropositivity (0.33 [95% CI 0.05, 0.61]) but had no significant relationship with HIV seropositivity (0.15 [95% CI −0.19, 0.50]). A history of criminal justice involvement was positively associated with syphilis seropositivity (0.25 [95% CI 0.06, 0.44]) but had no significant association with HIV seropositivity (0.19 [95% CI −0.10, 0.48]).

Table 3.

Bivariate probit regression analysis of factors associated with syphilis (N = 606), uConnect Study, Chicago.

Variable	Any syphilis			Any HIV
Variable	N(%)	Univariable coefficient (95% Confidence interval)	Multivariable coefficient (95% Confidence interval)	N(%)	Univariable coefficient(95% Confidence interval)	Multivariable coefficient(95% Confidence interval)
Age 19–20 years	20 (17%)	0.69(0.22, 1.16)**	0.72 (0.18, 1.25)*	24 (21%)	0.28(−0.34, 0.89)	−0.44(−1.44, 0.55)
Age 21–24 years	105 (39%)	1.40(0.7, 2.07)***	1.40(0.68, 2.13)***	99 (37%)	0.78(−0.04, 1.60)	0.14(−0.91, 1.19)
Age 25+ years	74 (43%)	1.45(0.92, 1.98)***	1.34(0.75, 1.94)***	84 (49%)	1.22(0.48, 1.97)**	0.37(−0.47, 1.20)
Associate’s degree or technical/vocational degree^a	55 (44%)	0.62(0.30, 0.94)***		61 (49%)	0.26(−0.59, 1.12)
Straight^b	5 (23%)	−0.90(−1.48, −0.32)**	−0.65(−1.21, −0.09)*	4 (18%)	−1.48(−1.98, −0.97)***	−1.16(−1.83, −0.49)**
Bisexual^b	45 (27%)	−0.20(−0.53, 0.13)	0.01(−0.33, 0.36)	38 (23%)	−0.52(−1.02, −0.03)*	−0.32(−0.91, 0.27)
Not close to gay community^c	18 (24%)	−0.56(−0.99, −0.11)*	−0.51(−0.99, −0.03)*	17 (22%)	−0.37(−0.99, 0.25)	−0.19(−0.72, 0.35)
No marijuana sex-drug use	42 (27%)	−0.42(−0.82, −0.01)*	−0.09(−0.61, 0.43)	45 (29%)	−0.45(−0.97, 0.07)	−0.51(−0.96, −0.06)*
Heavy marijuana used	81 (42%)	0.46 (0.13, 0.79)**		77 (39%)	0.23(−0.03, 0.49)
Sex with a transgender woman	12 (21%)	−0.53(−0.96, −0.10)*	−0.76(−1.27, −0.24)**	13 (23%)	−0.39(−0.98, 0.21)	−0.71(−1.16, −0.26)**
Group sex (past 12 months)	45 (41%)	0.15(−0.22, 0.52)		51 (46%)	0.50(0.20, 0.78)**
Engaged in exchange sex (past 12 months)	113 (40%)	0.31 (0.10, 0.52)**	0.20(−0.09, 0.49)	113 (40%)	0.22(−0.02, 0.46)	0.12(−0.46, 0.21)
Aware of sex partners’ HIV status	65 (50%)	0.44(0.21, 0.66)***		96 (73%)	1.52(1.12, 1.92)***
Used condoms as HIV risk reduction strategy	100 (28%)	0.29(−0.10, 0.69)	0.39(0.02, 0.76)*	51 (14%)	0.15(−0.32, 0.62)	0.22(−0.19, 0.63)
Any drug or alcohol use (last 12 months)	68 (46%)	0.45(0.09, 0.80)*		69 (46%)	0.46(0.24, 0.67)***
Sex within first 12 h of meeting partner	98 (38%)	0.18(−0.17, 0.53)		107 (41%)	0.36(0.13, 0.60)**
Socialized with other men at bars or clubs	134 (37%)	0.40(0.15, 0.65)**		150 (41%)	0.48(0.17, 0.81)**
Socialized with other men at gym	18 (27%)	−0.05(−0.49, 0.40)		12 (18%)	−0.77(−1.21, −0.32)***
Met sex partners using social media (previous 12 months)	152 (39%)	0.41(0.18, 0.64)***	0.33(0.05, 0.61)*	148 (38%)	0.26(0.04, 0.49)*	0.15(−0.19, 0.50)
Anorectal STI test (previous two years)	62 (40%)	0.20(−0.06, 0.47)		72 (46%)	0.39(0.16, 0.61)***
Had heard of PrEP	98 (40%)	0.23(−0.01, 0.47)		117 (48%)	0.54(0.31, 0.76)***
Had ever used PrEP	11 (50%)	0.16(−0.58, 0.91)		6 (27%)	−1.02(−1.76, −0.29)**
Criminal justice involvement^e	112 (40%)	0.42 (0.22, 0.62)***	0.25(0.06, 0.44)*	115 (41%)	0.49(0.25, 0.73)***	0.19(−0.10, 0.48)

PrEP: pre-exposure prophylaxis.

*P < 0.05; **P < 0.01; ***P < 0.001.

^aReference group is Grade 0–12.

^bReference group is gay sexual orientation.

^cReference group is ‘very close to gay community.’

^dReference group is ‘never used marijuana during sex.’

^eSubject has been detained, arrested, or spent time in jail or prison.

Several behaviors were found to have a negative association with syphilis and/or HIV. Among our study participants, self-identifying as straight as opposed to gay was negatively associated with syphilis seropositivity (−0.65 [95% CI −1.21, −0.09]) and HIV seropositivity (−1.16 [95% CI −1.83, −0.49]). Not feeling close to the gay community was negatively associated with syphilis seropositivity (−0.51 [95% CI −0.99, −0.03]) but had no significant relationship with HIV seropositivity (−0.19 [95% CI −0.72, 0.35]). Compared to always using marijuana during sex, never using marijuana during sex was negatively associated with HIV seropositivity (−0.51 [95% CI −0.96, −0.06]) but had no significant relationship with syphilis seropositivity (−0.09 [95% CI −0.61, 0.43]). Having had sex with a transgender woman had a negative association with syphilis seropositivity (−0.76 [95% CI −1.27, −0.24]) and HIV seropositivity (−0.71 [95% CI −1.16, −0.26]).

Discussion

Prior studies have characterized trends in syphilis prevalence with respect to age, race/ethnicity, and sexual behavior, and the increased prevalence of syphilis among Black MSM has been well documented.^2–4 Relatively little research, however, has further characterized factors associated with syphilis among a population-based cohort of YBMSM.

According to CDC 2016 surveillance data from the National Notifiable Diseases Surveillance System, MSM accounted for 80.6% of male P&S syphilis cases with information about sex of sex partners in 2016. Of MSM P&S syphilis cases, 36.8% were White and 29.1% were Black.¹ Our data demonstrate overall weighted prevalence of syphilis seropositivity of 17% among HIV-negative YBMSM; however, the overall weighted prevalence of syphilis seropositivity was 54% among HIV-positive YBMSM. Further, among HIV-positive men in our cohort, the rate of syphilis seropositivity among those aged 21–24 (60.9%) is higher than those aged 25–29 (52.6%). While not a direct comparison to the CDC 2016 surveillance data, our findings are consistent with national trends, which show youth aged 15–24 years are now experiencing increasing rates of syphilis seropositivity.¹ While HIV diagnoses among MSM could be prompting providers to screen more frequently for syphilis, YBMSM – who are among the most vulnerable groups affected by STIs – are disproportionately burdened with syphilis. This provides further support to the importance of improving implementation of current CDC guidelines for syphilis screening and testing to facilitate appropriate treatment and thereby reduce the disease burden within this high-risk population. This would require an integrative approach, taking into consideration systemic barriers such as inadequate access to healthcare services, poverty, and social marginalization, which disproportionately affect both sexual and racial/ethnic minorities – particularly young MSM – and create barriers to prompt diagnosis and medical treatment.

In our study, behaviors associated with increased probability of HIV seropositivity did not necessarily correlate with increased syphilis serostatus and vice versa. For example, we found that participants who self-reported not feeling close to the gay community and participants who self-identified as straight were less likely to be syphilis seropositive but had no difference in HIV infection rates. In contrast, abstinence from marijuana during sex was negatively associated with HIV seropositivity but had no significant association with syphilis seropositivity.

Previous studies have demonstrated increased risk of acquiring STIs with regular marijuana use in HIV-positive MSM.¹² While our univariate analysis found a significant positive association with marijuana use and both HIV seropositivity and syphilis seropositivity, this was not found to be significant in multivariable models. We did find, however, that never using marijuana during sex was negatively associated with HIV seropositivity when compared to always using marijuana during sex. These findings highlight the importance of collecting marijuana use history during harm reduction counseling with patients around HIV prevention.

Among our study sample of YBMSM in Chicago, using social media/internet to meet sexual partners was significantly correlated with syphilis seropositivity but not HIV seropositivity. An emphasis on syphilis testing and treatment among YBMSM regardless of HIV status might be an effective way to reduce the overall burden of syphilis seropositivity within this population. Previous studies have found that despite having a higher risk of contracting syphilis, MSM are not routinely tested for syphilis, even when they present for HIV testing.^11,12

Our findings that using condoms more often with the intention of reducing the risk of contracting HIV was positively associated with syphilis seropositivity but not HIV seropositivity are perhaps counterintuitive. One possible explanation for our findings is that syphilis is also transmitted via oral sex, and syphilitic lesions may be present in areas not protected by condoms. In addition, harm reduction practices tend to cluster and purposeful condom use may be associated with oral sex as a risk reduction practice. Privileging oral sex or use of oral sex during exchange sex may be important factors in syphilis acquisition. These findings emphasize the need to counsel patients on the risk of syphilis from nonpenetrative sex practices.

Previous research has elucidated the disparate rates of HIV prevalence among different racial/ethnic groups of MSM, with Black MSM having higher rates than non-Black Latino MSM and white MSM.¹³ Among Black MSM, previous research has shown non-gay-identified Black MSM have lower rates of HIV seropositivity, less sexual behavior with men, and more sexual behavior with women compared to gay-identified Black MSM.^14,15 Our finding that self-identifying as straight was negatively associated with HIV seroprevalence is in concordance with those findings. Prior studies have shown that Black MSM are more likely than white MSM to have STIs.^2,3,16 However, our findings that straight-identified YBMSM and YBMSM who do not feel close to the gay community have a lower likelihood of syphilis seropositivity highlight the importance of a closer examination of the sexual networks in which these men find sexual partners, if and under what circumstances they use condoms, and what harm reduction strategies they practice may clarify these findings. An understanding of their sexual networks also has important implications from a public health perspective when developing HIV and STI prevention strategies targeted toward YBMSM populations.

There are limited data on syphilis and HIV prevalence among transgender women in the United States due to the low overall inclusion of transgender persons in HIV/STI research.^17,18 Nonetheless a previous study by Deutsch et al.¹⁷ found that compared with MSM, transgender women who have sex with men more frequently reported transactional sex, receptive anal intercourse without a condom, or more than five partners in the past three months. These behaviors have been shown to correlate with increased risk of syphilis and HIV among other high-risk populations.^19,20 It would be reasonable to hypothesize that having sex with transgender women who have sex with men increases risk of syphilis acquisition or HIV. However, among our study population, having sex with transgender women appears to have a significant negative association with both syphilis seropositivity and HIV seropositivity. This has not been previously demonstrated and warrants further investigation.

Previous criminal justice involvement was positively associated with syphilis seropositivity but had no significant association with HIV seropositivity in our multivariate models. As previously discussed, there are likely systemic barriers in addition to sexual network distinctions that contribute to this difference. For example, racial differences in criminal justice involvement in the general US population are present among MSM. Additionally, history of arrest has been associated with condomless sex²¹ and it is unclear whether nonpenetrative sex such as oral sex is higher within criminal justice-involved populations. Future research investigating the relationship between criminal justice involvement and syphilis risk among YBMSM is needed.

While there were several notable findings, these analyses have several limitations. First, the use of a serum Treponemal antibody test in the absence of a non-Treponemal titer or information on past syphilitic infections and treatment is a significant methodological limitation. We are unable to stage cases of syphilis in this study; therefore, we cannot make a direct comparison to the CDC 2016 surveillance data, which are limited to P&S syphilis cases. The inability to identify whether the positive Treponemal antibody indicates prior successfully treated syphilitic infections or incident syphilitic infections prevents us from establishing temporality with respect to these reported behaviors and timing of syphilitic infection. However, the rate of syphilis seropositivity among HIV-positive men in our cohort aged 21–24 years was higher than the rate of syphilis seropositivity among older HIV-positive men in our cohort aged 25–29 years. Therefore, even if these estimates represent successfully treated cases of syphilitic infection, these data suggest that HIV-positive YBMSM in our cohort are acquiring syphilis at young ages at a disproportionate rate relative to the general population, even among MSM.

Another limitation is a variety of socioeconomic and societal factors unmeasured by our study also act to concentrate HIV in disadvantaged populations, of which young Black men make up a disproportionately large segment.²² The social status of the study participants as both racial/ethnic minorities and sexual minorities compels us to interpret these data carefully in order to avoid making broad generalizations about all young Black MSM.

Studies employing RDS strategies are also subject to potential biases. With RDS, the nonrandom selection of seeds could affect the characteristics of the study population by preferentially selecting higher risk individuals within networks.¹⁶ In an effort to improve engagement among a diverse group of YBMSM, seeds were selected from four kinds of venues either through referral from HIV program personnel (e.g. case manager) or through the posting of fliers referencing the study.

In conclusion, these data from uConnect build on existing formative research focused on disparities in syphilis seropositivity among MSM. Our study results suggest young Black MSM bear a significant disease burden with respect to syphilis seropositivity. Attention should be paid to strategies beyond expanding condom use since syphilis can be transmitted through nonpenetrative sex, which is often employed as an HIV prevention intervention. Studies on how to effectively implement routine syphilis screening and treatment for young Black MSM are also needed to address this disparity.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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Centers for Disease Control and Prevention (CDC). 2016 sexually transmitted diseases surveillance, https://www.cdc.gov/std/stats16/ (2017, accessed 19 November 2017).

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