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. 2026 Sep 29;21(9):e0358578. doi: 10.1371/journal.pone.0358578

Exploring the relationship between HIV Testing frequency and sexual behavior, prevention prophylaxis use among MSM in Southern China

Yinxia Liang 1, Min Wang 2, Yun Zhang 3, Jinli Mo 2, Weiyi Tian 3, Haimei Huang 1, Jiawen Zhu 2, Yangfang Wang 3, Hongbin Peng 1, Xia Luo 3, Ping Cen 1,*, Chuanyi Ning 3,4,*
Editor: Yury E Khudyakov5
PMCID: PMC13623135  PMID: 42809564

Abstract

Aim

This study aimed to explore the association between HIV testing trajectories, sexual behavior characteristics and HIV exposure prevention prophylaxis use, to provide a basis for developing more precise HIV prevention strategies.

Study design

This analysis utilized pseudonymized data from a three-arm, open-label randomized controlled trial (RCT) conducted in Guangxi, China, between 2021 and 2023.

Methods

This prospective cohort study enrolled 327 participants from southern China. Longitudinal data—including HIV testing, sexual risk behaviors, and prophylaxis use (PrEP/PEP)—were collected at baseline and quarterly for one year. Group-based trajectory modeling (GBTM) was used to identify behavioral patterns, and person-years (PY) of follow-up were calculated to estimate incidence densities of PrEP/PEP use and STI occurrence.

Results

A total of 76.45% of men who have sex with men (MSM) received HIV testing less frequently than once every three months, and HIV self-testing (HIVST) was not significantly associated with increased rates of HIV testing (HT). In the HT model, MSM who underwent middle-frequency HT were less likely to report having fewer temporary sexual partners (OR 0.120, 95% CI 0.017–0.85, P = 0.034) and regular sexual partners (OR 0.502, 95% CI 0.267–0.943, P = 0.032). The use of PrEP increased with higher HT frequency, demonstrating a 3.39-fold (95% CI: 1.377–8.843, P = 0.008) increase in the middle frequency group and a 7.335-fold (95% CI: 2.505–21.475, P < 0.001) increase in the high frequency group compared to the low frequency group. PEP use also increased with higher HT frequency, showing a 6.129-fold (95% CI: 1.921–19.553, P = 0.002) increase in the high frequency group compared to the low frequency group.

Conclusions

While frequent HIV testing demonstrates significant associations with increased sexual partner numbers, its role in facilitating consistent use of HIV exposure prevention prophylaxis remains clinically valuable.

Introduction

HIV prevalence among men who have sex with men (MSM) remains disproportionately high across global populations. The median HIV prevalence among MSM is significantly higher at 7.5%, nearly ten times the global median. Between 2006 and 2022, the share of new HIV diagnoses among MSM in China expanded dramatically from 2.5% to over one-quarter (25.6%) of total cases [1]. Despite ongoing initiatives to manage HIV, factors such as multiple sexual partners, widespread unprotected sex, and recreational substance use have contributed to an increase in new HIV cases among MSM in the country [2]. Consequently, there remains an urgent need to enhance investment in HIV prevention strategies targeting this population.

HIV testing (HT) serves as a fundamental component of prevention strategies by enabling early detection and timely initiation of treatment, thereby reducing transmission risks [3]. Studies demonstrate that regular testing significantly decreases HIV spread within MSM populations [4]. For MSM, a particularly high-risk group, the Centers for Disease Control and Prevention recommends testing at least once a year, with more frequent testing advised for individuals with multiple sexual partners and high levels of sexual activity [5]. However, the popularity and compliance of HT among MSM are not ideal. An Australian study indicated that HIV retest rates among MSM were below 40% after one year and below 20% after six months [6]. Furthermore, a study conducted in Guangzhou, China, revealed that only 44% of MSM were regularly tested for HIV [7]. Despite progress in HT coverage, only 61.2% of Chinese MSM had confirmed their serostatus by 2022, underscoring the need for enhanced testing promotion strategies [8]. HIV self-testing (HIVST) represents an innovative approach to expanding HT coverage [9]. Previous meta-analyses have consistently demonstrated that HIVST doubles the frequency of testing compared to site-based HIV testing (SBHT) [10,11]. The World Health Organization (WHO) recommends HIVST as a strategy to enhance the accessibility of HT for individuals at elevated risk.

Additionally, HT serves as a crucial gateway to additional prevention services, including both pre- and post-exposure prophylaxis (PrEP/PEP) interventions. PrEP and PEP have proven effective in preventing HIV infection in this population and are currently being promoted and implemented in numerous countries in accordance with WHO guidelines [12]. Despite significant efforts to advance HIV prevention services, marginalized groups in China and globally continue to experience inadequate service coverage [13, 14]. Globally, just 50.0% and 58.6% of MSM are informed about and open to using PrEP [14], whereas 51.6% and 6.0% of MSM are familiar with and have taken advantage of PEP[13]. Despite 70% awareness levels documented in a three-year cross-sectional Chinese study, utilization rates for these prevention tools remained below 30% (PrEP) and 25% (PEP) in MSM populations [15]. A meta-analysis from China also pointed out similar results [16]. Therefore, further investigation is warranted to elucidate existing obstacles and enhance service accessibility for PrEP-eligible MSM populations.

This study aimed to evaluate the use of HIV exposure prophylaxis (PrEP/PEP) and, as a secondary objective, the occurrence of STIs among MSM, while analyzing the relationships between these factors and HT frequency trajectories. Additionally, we assessed unprotected sexual intercourse, the number of sexual partners. It is anticipated that this study will provide a scientific basis and practical guidance for optimizing HIV prevention and control strategies, enhancing the compliance and popularity of PEP and PrEP, and informing the development of subsequent research content and methodologies.

Methods

Study design and data source

For this research, we compiled pseudonymized data from a three-arm, open-label randomized controlled trial that was conducted in parallel from 2021 to 2023; Baseline recruitment was conducted from September 1, 2021, to February 28, 2022. Participants completed follow-up visits at 3, 6, 9, and 12 months after baseline. The final follow-up was completed by February 28, 2023 (12 months after the last enrolled participant). The maximum follow-up duration was 12 months for all participants [17]. The complete methodology of the study has been detailed in previous publications. In summary, HIV-negative MSM were eligible to participate if they met the following criteria within the six months prior to enrollment: (1) they had engaged in anal intercourse with another male at least once; (2) they received a negative result for syphilis through rapid testing; and (3) they were residents of Guangxi, China, without intentions to leave the area for the subsequent 12 months.

Every participant received HT and was set for follow-up appointments every three months for a maximum duration of one year (until February 2023) to assess medication status in relation to HIV exposure prophylaxis, monitor STI infection status, and evaluate risk behaviors over time. For inclusion in this analysis, participants were required to have completed a behavioral questionnaire during at least one baseline and one follow-up study visit.

Variables of interest

Outcome variable.

The primary outcome measure was the use of HIV exposure prophylaxis, encompassing both PrEP and PEP. Secondary outcomes included the incidence of STIs, the frequency of HT (including both HIVST and SBHT), the number of sexual partners (both regular and casual), and the frequency of unprotected sexual behavior.

Exposure variables.

Exposure variables included age, education level, occupation, monthly income, marital status, all of which were collected during the baseline interview. Additionally, data on the use of addictive substances (such as RUSH and Viagra) over the past six months, as well as sexual behavior characteristics—including age at first sexual encounter, number of sexual partners in the past six months, frequency of unprotected sex among MSM during this period, sexual role, positive sexual partners, and incidents of condom rupture—were also recorded.

Definition of trajectory groups

Longitudinal changes in repeated measures of behaviors related to sexual activity and HIV testing (including HIVST and SBHT) were examined using group-based trajectory modeling (GBTM) [2,18,19]. Details regarding this procedure can be found in the Data Supplement. The quantity of groups (trajectories) and their categorizations for each outcome were extrapolated from prior research concerning MSM sexual behavior and HT behavior, in addition to certain professional standards [18,20]. HIV testing frequency was categorized based on recommendations from multiple international guidelines. The WHO (2019) recommends annual testing for sexually active MSM and 3–6 monthly testing for those at increased risk [21]; the US CDC (2025) recommends annual screening for MSM, with more frequent testing (every 3–6 months) for high-risk individuals [22]; and the IAS-USA (2024) advises 6-monthly HIV testing for PrEP users and 3-monthly testing for frequently exposed individuals [23]. Accordingly, we defined: Low (<1 test/3 months), Medium (1–2 tests/3 months), and High (≥3 tests/3 months).

Statistical analysis

GBTM employs finite mixture modeling to identify distinct population subgroups characterized by unique trajectories for one or more outcomes of interest [24]. The optimal trajectory group count was determined by simultaneously minimizing Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) values while maximizing mean posterior assignment probabilities, the minimum acceptable posterior assignment probability for trajectory group membership was set at ≥0.8 [25–27]. Although our pre-specified minimum group size was 5%, the 4.8% and 4.91% proportions represent slight deviations due to model optimization based on BIC. We conducted sensitivity analyses with alternative model specifications (2-group and 4-group solutions), which confirmed the presence of a distinct high-frequency group (see Supplementary S1 Table). The original 3-group solution was retained because it provided the best fit to the data (lowest BIC) and clinical interpretability. We achieved parsimonious models by omitting polynomial terms (trajectory shapes) that did not reach statistical significance (p < 0.05). STI incidence and PrEP/PEP utilization rates were derived using person-time analysis, expressed as events per 100 person-years (PY) of follow-up. Confidence intervals (CIs) for these rates were calculated using the Poisson distribution, and a Cox regression model was utilized to compare and analyze the occurrence of events.

Sensitivity analysis

Missing responses resulted in infrequent missing values (<5% for each variable) and were retained unchanged. The trajectory group modeling utilized SAS software version 9.4 (SAS Institute). For the additional analyses and visualizations, R version 4.3.0 was employed alongside the ggplot2 package.

Ethical approval for this study (No. 20210173) was granted by the Institutional Review Board at Guangxi Medical University in China. The raw data supporting the findings of this study are not publicly available due to the sensitive nature of the information collected (including sexual behavior and HIV status), which could compromise participant privacy. Data requests may be directed to the Institutional Review Board at Guangxi Medical University (gxmuyfyll@163.com), which will review requests for data access in accordance with the ethical approval granted for this study.

Results

Characteristics of study participants

Among the 330 participants enrolled, 327 (99.90%) completed at least one behavioral questionnaire and participated in this analysis (see Table 1). The average age was 23.3 years (standard deviation 11.3), with 181 participants (55.35%) being under 30 years old. Of the participants, 98 (29.97%) were students, and 293 (89.60%) were unmarried. Nearly a quarter of MSM have used addictive drugs in the past 6 months, 9.17% (30/327) of the MSM had ever been infected with STIs. The majority of MSM underwent HT in the past year (85.02%), and 146 MSM utilized HIVST during that period. A total of 256 MSM (78.29%) reported having between 1–5 male sexual partners in the past six months, while 185 (56.41%) MSM engaged in unprotected sexual behavior, and 90 MSM experienced condom breakage during the same period. Furthermore, 43 (13.15%) MSM reported having sexual partners who were HIV-positive, and 90 (27.52%) MSM experienced condom breakage.

Table 1. Enrolment characteristics of participants (N = 327).

Variable Description[n(%)] Variable Description[n(%)]
Age (year) 181 (55.35) SBHT (past 6 months)
 <30 107 (32.72) Yes 278 (85.02)
 30-40 39 (11.93) No 49 (14.98)
 >40 HIVST (past 6 months)
Medical insurance Yes 143 (43.59)
 Yes 285 (87.16) No 185 (56.41)
 No 42 (12.84) STI
Education Yes 30 (9.17)
 High school or below 73 (22.32) No 297 (90.83)
 College and undergraduate 238 (72.78) Age of first sexual intercourse (year)
 Graduate students and above 16 (4.90) <18 74 (22.63)
Employment 18-30 236 (72.17)
 Student 98 (29.97) >30 17 (5.20)
 Non-student 229 (70.03) Number of sexual partners (past 6 months)
Monthly income (Chinese Yuan) 0 32(9.79)
 <1500 59 (18.04) 1-5 256 (78.29)
 1500-3000 68 (20.80) 6-30 39 (11.92.)
 3001-5000 96 (29.36) Sex role
 5001-8000 79 (24.16) Inserter 104 (31.81)
 <8001 25 (7.64) Inserted party 100 (30.58)
Marital status Inserter/Inserted party 123 (37.61)
 Unmarried. 293 (89.61) Positive sex partner in the past 6 months
 Married. 23 (7.03) Yes 43 (13.15)
 Divorced. 11 (3.36) No 230 (70.34)
Sexual orientation Uncertain 54 (16.51)
 Gay 221 (67.58) Condomless anal sex with men (past 6 months)
 Bisexual 84 (25.69) Yes 182 (55.66)
 Uncertain 22 (6.73) No 145 (44.34)
Biological gender identity Drug use
 Yes 286 (87.46) Yes 82 (25.08)
 No 41 (12.54) No 245 (74.92)
Disclosure of sexual orientation
 Yes 82 (25.08)
 No 245 (74.92)

SBHT: Site-based HIV testing. HIVST: HIV self-testing. STIs: Sexually transmitted infections

Description of trajectories

We employed a cohort-based trajectory model to analyze HT behaviors, including both HIVST and SBHT, and the number of sexual partners (both casual and fix) and instances of unprotected sexual behavior. Trajectories 1–4 were identified in this analysis (S1 Table). We found three different behavioral trajectories of TH (Fig 1A). Approximately 77.75% of the 327 participants used HT an average of once every three months or less (referred to as “low frequency”). Meanwhile, 17.45% tested an average of twice every three months, with some variation around this average (“middle frequency”), and 4.80% tested more than average of three times every three months (“high frequency”). In terms of SBHT and HIVST, two groups were identified: 82.56% tested less than 0.5 times every three months (low frequency), while 17.44% tested more than once every three months (indicating a gradual increase in frequency). Additionally, 82.46% were tested less than 0.5 times every three months (low frequency), and 17.54% were tested more than twice every three months, showing minimal variation (middle frequency) (Fig 1B and C). In the modeling of sexual partners, three distinct probability trajectories were identified: high (4.91%), multiple sexual partners (16.56%), and low (78.53%) (Fig 2A). As shown in Fig 2(B),As illustrated in Fig 2, a majority of MSM maintained low levels, representing 94.79% of instances with one or no casual sex partners in a three-month period. As shown in Fig 2(D). In the model of unprotected sexual behavior, we found that most MSM (86.12%) engaged in unprotected sexual behavior less than once every three months. A smaller number of MSM (5.99%) exhibited increased unprotected sexual behavior over time, while another small group (7.89%) demonstrated a decrease in unprotected sexual behavior over the same period.

Fig 1. (A) HT: HIV testing.

Fig 1

(B) SBHT: HIV facility-based testing. (C) HIVST: HIV self-testing. Low: < 1 test/3 months. Middle: 1–2 tests/3 months. High: ≥ 3 tests/3 months.

Fig 2. (A) Sexual partner, (B) Fixed sex partner, (C) Casual sex partner: Low: Less than 1 sexual partner every 3 months.

Fig 2

Middle: 1-5 sexual partners every 3 months. High: ≥ 6 sexual partners every 3 months. (D) Unprotected sexual intercourse: Low: Unprotected sex < 1 times every 3 months. Middle: Unprotected sex 1-5 times every 3 months. High: Unprotected sex ≥ 6 times every 3 months.

Determinants of HT trajectory membership

In the HT model, participants with “high frequency” HT had sex with men more than 6 times in the past 6 months compared to the other trajectories (p = 0.019). In the SBHT model, Participants with income between “5000 - 8000” RMB were divided into “middle frequency” group (p = 0.022). In the HIVST model, MSM in the middle-frequency group were younger (p = 0.020) and had a higher proportion of students compared to those in the low-frequency group (p = 0.008). Additionally, there was a notable prevalence of substance use (p = 0.007) and unprotected sex (p = 0.038) reported in the last six months. (S2 Table)

HT and sexual behavior trajectories

In the HT model, MSM who had fewer casual (0.120, 0.017–0.857, P = 0.034) and fix (0.502, 0.267–0.943, P = 0.032) sexual partners were less likely to engage in “moderate frequency” HT compared to “low frequency” trajectories (see Table 2). Similar results were observed in the SBHT model, MSM who had fewer casual (0.105, 0.017–0.670, P = 0.017) sexual partners were less likely to engage in “moderate frequency” (see Table 3)

Table 2. Relationship between HIV testing trajectory, number of sexual partners, and unprotected sex trajectory.

Variable Low HT* Middle HT* High HT* Low SBHT Middle SBHT$ Low HIVST Middle HIVST&
aOR (95% CI) P OR (95% CI) P aOR (95% CI) P aOR (95% CI) P
Trajectory of sexual partners
 Low 1.000 5.887 (0.575 - 60.286) 0.135 0.501 (0.022 - 11.582) 0.666 1.000 1.650 (0.213 - 12.770) 0.632 1.000 11.193 (0.597 - 209.790) 0.106
 High 1.000 1.000 1.000 1.000
Trajectory of fixed sex partners
 Low 1.000 0.120 (0.017 - 0857) 0.034 0.267 (0.013 - 5.647) 0.397 1.000 0.105 (0.017 - 0.67) 0.017 1.000 0.285 (0.035 - 2.328) 0.206
 High 1.000 1.000 1.000 1.000
Trajectory of casual sex partners
 Low 1.000 0.502 (0.267 - 0.943) 0.032 0.485 (0.170 - 1.381) 0.175 1.000 0.680 (0.352 - 1.314) 0.251 1.000 0.680 (0.352 - 1.314) 0.251
 High 1.000 1.000 1.000 1.000
Trajectory of unprotected sexual intercourse
 Low 1.000 0.929 (0.178 - 4.850) 0.930 0.748 (0.055 - 10107) 0.827 1.000 3.306 (0.507 - 21.545) 0.211 1.000 0.521 (0.079 - 3.421) 0.497
 Middle 1.068 (0.353 - 3.231) 0.908 0.724 (0.139 - 3.762) 0.700 2.301 (0.500 - 10.580) 0.284 0.952 (0.307 - 2.949) 0.932
 High 1.000 1.000 1.000

*Adjust for frequency of unprotected sex in the past 6 months. $: Adjust for frequency of unprotected sex in the past 6 months. &: Adjustment of occupation, amount of money at your disposal each month, whether you have used drugs in the last 6 months, and have had unprotected sex with men in the last 6 months. Sexual partner: Low: Less than 1 sexual partner every 3 months. Middle: 1–5 sexual partners every 3 months. High: ≥ 6 sexual partners every 3 months. Unprotected sexual intercourse: Low: Unprotected sex < 1 times every 3 months. Middle: Unprotected sex 1–5 times every 3 months. High: Unprotected sex ≥ 6 times every 3 months. HT: HIV testing. SBHT: HIV facility-based testing. HIVST: HIV facility-based testing. Low: HIV testing frequency is less than once every 3 months. Middle: HIV testing frequency 1 times every 3 months. High: HIV testing frequency ≥ 2 times every 3 months.

Table 3. STI incidence, PrEP and PEP incidence rates and risk for the assigned sexual and HIV testing trajectory groups.

Probability trajectory STI incidence rate/100 PY STI incidence rate ratio p-Value PrEP incidence rate/100 PY PrEP incidence rate ratio p-Value PEP incidence rate/100 PY PEP incidence rate ratio p-Value
Overall
 (n = 327) 7.65 (5.11, 11.21) 7.03 (4.61, 10.51) 7.65 (5.11, 11.21)
HIVST
 Low 7.60 (4.76, 11.80) 4.80 (2.69, 8.26) 5.17 (2.96, 8.71)
 Middle 5.85 (1.32, 15.06) 0.668 (0.198, 2.257) 0.516 17.86 (9.34, 30.85) 3.88 (1.70, 8.84) 0.001 7.14 (2.31, 18.13) 1.41 (0.46, 4.27) 0.548
SBHT 16.67 (4.41, 42.27) 2.128 (0.630, 7.191) 0.224
 Low 6.57 (4.05, 10.36) 3.28 (1.61, 6.36)
 Middle 7.30 (4.63, 11.22) 9.43 (3.53, 21.42) 1.451 (0.539, 3.908) 0.461 16.98 (8.52, 30.30) 5.370 (2.131, 13.531) <0.001
HT 9.43 (3.53, 21.42) 1.318 (0.495, 3.512) 0.581
 Low 4.00 (2.05, 7.46) 4.00 (2.05, 7.46)
 Middle 6.27 (3.81, 10.04) 13.56 (6.45, 25.53) 3.39 (1.377, 8.843) 0.008 6.78 (2.19, 17.27) 1.725 (0.541, 5.500) 0.357
 High 14.29 (6.80, 26.78) 2.29 (0.98, 5.31) 0.053 27.78 (10.71, 53.59) 7.335 (2.505, 21.475) <0.001 22.22 (73.72, 48.08) 6.129 (1.921, 19.553) 0.002

HT: HIV testing. SBHT: HIV facility-based testing. HIVST: HIV facility-based testing. Low: HIV testing frequency is less than once every 3 months. Middle: HIV testing frequency 1 times every 3 months. High: HIV testing frequency ≥ 2 times every 3 months.

Use of HIV exposure prophylaxis

Overall, among 327 participants, 23 MSM reported using PrEP during follow-up (Table 3). The incidence of PrEP use was 7.03 per 100 PY (95% CI: 4.61, 10.51). In the HT model, PrEP use increased with higher HT frequency, showing a 3.39-fold (95% CI: 1.377–8.843, P = 0.008) increase in the middle frequency group and a 7.335-fold (95% CI: 2.505–21.475, P < 0.001) increase in the high frequency group compared to the low frequency group. In the HIVST model, PrEP use in the middle-frequency HT group was 3.88 times higher than in the low-frequency HIVST group (95% CI: 1.70–8.84, P = 0.004). However, similar results were not observed in the SBHT model. And, among 327 participants, 18 MSM reported using PEP during follow-up (Table 3). The incidence of PEP use was 7.65 per 100 PY (95% CI: 5.11, 11.21). In the HT model, PEP use increased with higher HT frequency, showing a 6.129-fold (95% CI: 1.921–19.553, P = 0.002) increase in the high frequency group compared to the low frequency group. In the SBHT model, PEP use in the middle-frequency group was 5.370 times higher than in the low-frequency SBHT (95% CI: 2.131–13.531, P < 0.001). However, similar results were not observed in the HIVST model.

Incidence and risk of STI

Overall, 25 cases of STIs were reported among 327 participants (Table 3). The STI incidence was 7.65 per 100 PY (95% CI: 5.11, 11.21). In the HT model, participants in the high-frequency HT group experienced an increased STI incidence of 16.67 (95% CI: 4.41, 42.27). Similar findings were observed in both the SBHT model and the HIVST model. Notably, Cox regression analysis indicated that the incidence of STIs in the middle-frequency HIVST was 2.29 times (95% CI: 0.98, 5.31; P = 0.053) that of the low-frequency HIVST.

Discussion

This study examines the role of HIVST in expanding HT and investigates the relationships between HT, SBHT, HIVST, and the incidence of unprotected sex, number of sexual partners, and HIV exposure prevention among MSM in a longitudinal cohort in southern China. The results indicate that only a small proportion of MSM engaged in regular HT, defined as testing more than once every three months on average, and the positive impact of HIVST on expanding HT was not observed. Participants in high-frequency HT groups reported a greater number of sexual partners, higher rates of sexually transmitted infections, and increased utilization of HIV exposure prevention measures. These findings highlight the critical need to promote regular HT and enhance high-frequency surveillance among MSM while ensuring timely access to HIV exposure prevention strategies.

To further contextualize these findings, we examined descriptive trends in key outcomes from baseline to 12-month follow-up (Table 3). These data showed sustained HIV testing engagement during follow-up, with 63.30%–68.50% of participants testing at least once per 3 months. However, PrEP and PEP use during follow-up remained low, ranging from 3.98% to 5.50% and 1.83% to 3.06%, respectively. Meanwhile, the proportion of participants reporting unprotected sexual behavior remained relatively stable across follow-up, ranging from 21.71% to 26.60%. Notably, 22 new STI cases were diagnosed during the 12-month follow-up, in addition to 5 participants with STI at baseline. These findings underscore the ongoing STI burden and the need for integrated HIV/STI prevention services, particularly given the sustained level of unprotected sexual behavior observed throughout the follow-up period.

HT is a critical first step in both prevention and treatment efforts. It is essential for determining an individual's HIV status and initiating appropriate treatment [28]. However, in our analysis, 76.45% (250 out of 327) of MSM received HIV test less than once every 3 months. Adherence to regular HIV treatment among MSM may be low [6]. This may be attributed to social prejudice and a lack of awareness about HIV, which can create feelings of shame among many MSM, ultimately leading to resistance to testing and a tendency to avoid it [29–31]. Additionally, insufficient medical resources and limited accessibility to testing services make regular testing inconvenient, reducing the likelihood of participation [32–34]. Technological progress has advanced surveillance methods for MSM, and HIVST has emerged as a crucial complement to traditional HT in this population. In our analysis, only a minority of MSM reported conducting HIVST at least once every three months. Furthermore, HIVST was not significantly linked to increased rates of HT. But compared with SBHT in health care Settings, CDC clinics, and community-based organizations (Cbos), HIVST offers advantages in terms of privacy, confidentiality, and convenience [35], despite the finding in our analysis that over time, Some MSM did have an increase in the frequency of HT, and this increased frequency was associated with an overall rise in HT. But the coverage of SBHT services varies by socioeconomic level. As a complementary approach to SBHT, HIVST can help reduce public health disparities and increase HT coverage among MSM. For instance, digital tools have shown promise in improving HIV testing uptake among MSM. a recent study demonstrated that a chatbot-delivered HIV self-testing service effectively increased testing rates among MSM [36]. Integrating such digital approaches into HIV prevention programs in southern China may complement facility-based testing and help address barriers such as stigma and privacy concerns.

The result indicating that a greater intensity of HT was not linked to alterations in unprotected sexual behavior aligns with earlier observations [37]. However, it was significantly linked to an increase in both casual and regular sexual partners. People who undergo regular HT may show higher awareness of safer sex. For example, studies have found that MSM who test regularly have higher rates of condom use during sex [38,39]. In addition, a high proportion of MSM would choose HT after having experienced multiple sexual partners or unsafe sexual behavior [40]. This finding was consistent across studies examining both HIVST and SBHT. Taken together, these results suggest that the frequency of HT, as well as the choice between self-testing and facility testing, may not significantly influence subsequent sexual behavior. HT practices are influenced by various contexts, including individual, interpersonal, community, and broader social factors. The presence or absence of social support among friends, peers, and the larger communities of gay men plays a significant role in determining men's testing behaviors [41]. The observation that high-frequency HT did not correlate with the incidence of HIV or STIs is significant. Since we did not detect a notable disparity in condom usage between individuals engaging in regular high-frequency HT and those with low-frequency HT, it is not surprising that the study also found no significant difference in HIV or STI incidence between these groups.

Our findings suggest that MSM with high frequency of HT are more likely to use PrEP/PEP compared with MSM with low frequency of HT. Previous studies have indicated that MSM who engage in frequent HT tend to exhibit higher risk awareness [42], possess strong knowledge and acceptance capabilities [43], demonstrate a greater willingness to engage in active prevention, and have improved access to medical resources [44]. Consequently, these individuals are more inclined to accept and utilize PrEP and PEP and maintain consistent usage. After conducting a subgroup analysis, we observed an intriguing phenomenon. MSM who self-tested for HIV with high frequency were more likely to utilize PrEP for prevention compared to those who self-tested infrequently. Similarly, MSM who underwent on-site HT with high frequency exhibited a stronger correlation with the use of PEP than their counterparts who tested on-site less frequently. MSM who frequently self-test for HIV demonstrate a heightened awareness of ongoing risk. Regular self-testing keeps them vigilant regarding the potential for HIV infection. The long-term and continuous use characteristics of PrEP align well with the need for sustained prevention. Additionally, the convenience and privacy associated with self-testing encourage MSM to engage in regular testing and opt for the equally convenient PrEP as a preventive measure [45]. On-site testing typically occurs following high-risk behavior, allowing MSM to receive professional recommendations and guidance. This frequent on-site testing underscores their need for prompt intervention after engaging in high-risk activities. As an emergency preventive measure, PEP effectively addresses this need for immediate prevention. We also observed that although age was correlated with HIVST frequency (younger MSM were more likely to be in the high-frequency self-testing group), we found no significant association between middle-frequency testing trajectories and PEP use. Potential barriers to linking self-testing to PEP for younger MSM include: (1) lack of awareness about PEP availability and access points [46]; (2) perceived low risk despite frequent testing behavior [42]; (3) cost concerns due to the high out-of-pocket expenses for PEP [47]; and (4) fear of disclosure and stigma when seeking PEP at clinics [48]. These barriers highlight the need for integrated interventions that combine HIV self-testing with PEP education and referral services. Future interventions should focus on integrating PEP education into HIV self-testing platforms (e.g., app-based referral systems) and establishing rapid, low-barrier pathways from self-testing to PEP services, particularly for younger MSM who demonstrate high risk awareness through frequent self-testing. HT and HIV exposure prevention are complementary in HIV prevention strategies. Especially the potential of HIVST and HIV pre-exposure prophylaxis among MSM, future research should continue to explore the integration model of the two to improve the effectiveness of HIV prevention and treatment.

Limitations

This research has multiple limitations. First, the study period (September 2021 to February 2023) overlapped with COVID-19 control measures in China. Although the study sites did not experience strict lockdowns during recruitment, local mobility restrictions and temporary clinic closures may have affected access to HIV testing and PrEP/PEP services for some participants. This could have led to an underestimation of HIV testing frequency and prevention service uptake. Nonetheless, readers should interpret the findings with consideration of this unique pandemic context. Second, participants were solely selected from Guangxi, China, which could result in limited representativeness and generalizability. In particular, our sample overrepresents younger, more educated MSM (mean age 23.3 years; 29.97% students). In comparison, a cohort study in Zhuhai reported that MSM aged 18–24 accounted for 23.18%, with students comprising only 6.62% [49]. A 28-province study (N = 2,618) reported 26.90% aged <25 years and 18.80% students [50], and a Northwest China study reported 16.3% aged 18–25 years with <8.1% students [51]. These comparisons suggest that our sample is significantly younger and more student-dominated than many other Chinese MSM cohorts, limiting generalizability to older MSM and non-student populations. Future studies should include more diverse age and occupational groups to validate our findings.Third, the results interpretation relies on self-reported questionnaires, potentially introducing biases related to reporting and recall. Moreover, the MSM group exhibits a high sensitivity concerning personal privacy and sexual behavior, which might result in hesitance to provide accurate information or engage in certain assessments during the study. Finally, our analysis employed GBTM to identify distinct testing trajectories and Cox regression to examine group differences in outcomes. This approach was chosen to address our primary research question of characterizing heterogeneity in testing patterns. However, we did not apply mixed-effects or GEE models to formally test within-person change over time. While our descriptive comparisons of baseline and follow-up outcomes provide some indication of overall change, formal growth curve models would offer more rigorous estimates of individual-level trajectories. Future studies should consider applying such methods to further characterize within-person changes in HIV testing and prevention behaviors.

Conclusion

Overall, while a high frequency of HT is associated with having multiple sexual partners and the occurrence of STIs, regular HT can facilitate the use of HIV prevention medications. Notably, PrEP use was more strongly associated with HIV self-testing, while PEP use was more closely linked to facility-based testing. These findings suggest that HIVST may be an effective entry point for PrEP implementation, whereas facility-based testing remains important for PEP access. Differentiated service delivery models should be developed to leverage the unique synergies between each testing modality and its corresponding prevention method.

Supporting information

S1 Table. Model fit assessment indicators for HIV testing and sexual partner/behavior trajectories in MSM.

(DOCX)

pone.0358578.s001.docx (23.9KB, docx)
S2 Table. Trajectory group characteristics of HIV testing patterns among MSM.

(DOCX)

pone.0358578.s002.docx (46.1KB, docx)
S3 Table. Descriptive changes in HT, HIVST, SBHT, PEP/PEP, unprotected sexual behavior from baseline to 12-month follow-up.

(DOCX)

pone.0358578.s003.docx (16.8KB, docx)

Acknowledgments

We would like to express our gratitude to all participants of this study, as well as the Nanning Center for Disease Control and Prevention, Nanning Green City Rainbow Center, and volunteers from Beihai, Liuzhou, Guilin, and Yulin for their support and assistance.

Data Availability

The raw data supporting the findings of this study are not publicly available due to the sensitive nature of the information collected (including sexual behavior and HIV status), which could compromise participant privacy. Data requests may be directed to the Institutional Review Board at Guangxi Medical University (gxmuyfyll@163.com), which will review requests for data access in accordance with the ethical approval granted for this study.

Funding Statement

This study was supported by the Outstanding Youth Fund of The Natural Science Foundation of Guangxi in China (Grant No. 2023GXNSFFA026007); The Natural Science Foundation of Guangxi in China (Grant No. 2023GXNSFAA026287); and The Science and Technology Project for Disease Control and Prevention of Guangxi in China (Grant No. GXJKKJ2025YB009). There was no additional external funding received for this study.

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Reviewer #2: Yes

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Reviewer #1: 1. Although this study uses a longitudinal cohort with repeated quarterly measures, the analysis primarily focuses on trajectory group membership and between-group differences. It is unclear how outcomes (e.g., HIV testing frequency, PrEP/PEP use, sexual behaviors) changed from baseline to follow-up within individuals. The authors should clarify whether and how within-person changes over time were assessed (e.g., baseline vs endline, time trends using mixed-effects or GEE models).

2. The manuscript reports recruitment between September 2021 and February 2022, with follow-up completed by February 2023, but elsewhere states that follow-up lasted “until March 2022.” These statements are inconsistent. The authors should clearly define: (a) what constitutes baseline, (b) the exact follow-up schedule (e.g., 3, 6, 9, 12 months), and (c) the maximum follow-up duration used in analyses.

3. The study period overlaps with COVID-19 control measures in China, which may have affected access to HIV testing and PrEP services among MSM. Although the authors state that study sites did not experience strict lockdowns during recruitment, variation in service availability over calendar time may still bias outcomes. The authors should more explicitly discuss this issue and, if possible, consider sensitivity analyses adjusting for calendar period.

4. The definitions of “low,” “middle,” and “high” HIV testing frequency are inconsistent between the main text and figure legend. These categories should be harmonized across the manuscript. In addition, the rationale for the chosen cut-points should be justified (e.g., based on guidelines, prior literature, or empirical distribution), and discussed in the main text.

5. The sample is relatively young and includes a high proportion of students, which may not fully represent the broader MSM population in China. The authors should compare baseline characteristics with other Chinese MSM cohorts and discuss implications for generalizability.

6. The terms “pretreatment” and “post-treatment” visits are unclear in the context of this cohort analysis and may imply an intervention effect. Please clarify what “treatment” refers to and whether trial arm assignment was accounted for in the analyses.

7. The authors may consider discussing digital tools in improving HIV testing, such as doi:10.1001/jamanetworkopen.2025.44821

8. Table 1 appears to contain potential internal inconsistencies (e.g., reporting zero sexual partners while also reporting a high proportion of HIV-positive partners). The authors should verify variable definitions and data coding.

Reviewer #2: Very nicely laid out and written manuscript. Would revise to focus on 'Use of PrEP" among trajectories as primary objective and STI as secondary. The only technical concern is that some of the subgroups trajectories fall below 5% of the study population which may indicate that alternative grouping strategies (different cut-offs or less groups) need to be considered. Conclusion should also reconcile differences between PrEP and PEP uptake.

A few specific comments below:

Abstract

Line #17 "men" not "man"

Manuscript

Introduction

- "INTRODUCTION" not INTRUDITION

- Lines 18 and 19, I believe that authors wanted to state that "retest" rates were less than 20%

- Line 42, aim in examining STI incidence is not consistent with abstract. STI is secondary outcome for this paper. Please revise if that was intention of this manuscript.

Methods

- Line 26, aim in examining STI incidence is not consistent with abstract. Use of PreP is. STI is secondary outcome for this paper. Please revise if that was intention of this manuscript.

Statistics

-Line 8, please include actual and minimum allowable posterior assignment probability (e.g. >0.8 was considered acceptable)

Results

- Line 4 and 11, please explain why high use of 4.8% and 4.91% of study population, respectively were allowed, when 5% was minimum in Methods

- Would reorder Incidence of STI and Use of HIV Exposure Prophylaxis actions

Discussion and Conclusion

I did not see statistics on condom use highlighted early in manuscript. Descriptive data should be laid out prior to discussing in conclusion. Also, per appendix, age is correlated with self-testing but middle trajectories not correlated with PEP, please include in your discussion on how this gap can be potentially addressed in the local context. What are potential bariers to linking ST to PEP for this age group which uses high rates of self-testing? Can this be explained?

**********

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Reviewer #1: No

Reviewer #2: No

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PLoS One. 2026 Sep 29;21(9):e0358578. doi: 10.1371/journal.pone.0358578.r002

Author response to Decision Letter 1


22 Jun 2026

Response to Reviewers

Manuscript ID: PONE-D-25-58406

Title: Exploring the Relationship Between HIV Testing Frequency and Sexual Behavior, Prevention Prophylaxis Use Among MSM in Southern China

Journal: PLOS ONE

Dear Dr. Bloom and Reviewers,

Thank you for the opportunity to revise and resubmit our manuscript to PLOS ONE. We sincerely appreciate the thoughtful and constructive comments from both reviewers, which have significantly improved the quality of our work. We have carefully addressed all concerns point-by-point as detailed below. All changes in the manuscript have been highlighted using track changes.

Journal Requirements

Response to Requirement 1 (Formatting): We have reformatted the manuscript according to the PLOS ONE style templates. The title page, author affiliations, main body, and references now follow the journal's formatting guidelines. All files have been named as requested.

Response to Requirement 2 (Funding Statement): We have amended the Funding Statement as follows:

“This study was supported by the Outstanding Youth Fund of the Natural Science Foundation of Guangxi in China (Grant No. 2023GXNSFFA026007); the Natural Science Foundation of Guangxi in China (Grant No. 2023GXNSFAA026287); and the Science and Technology Project for Disease Control and Prevention of Guangxi in China (Grant No. GXJKKJ2025YB00). There was no additional external funding received for this study.”

The amended statement has been included in the cover letter. All funding-related text has been removed from the manuscript.

Response to Requirement 3 (Funding in Manuscript): All funding-related content has been removed from the manuscript. Funding information now appears only in the online submission form.

Response to Requirement 4 (Data Availability Statement): We have updated the Data Availability Statement. The raw data supporting the findings of this study are available from the Institutional Review Board at Guangxi Medical University upon reasonable request. Due to participant privacy concerns (including sensitive information about sexual behavior and HIV status), data cannot be made publicly available. Requests for data access may be directed to the corresponding author or to the Institutional Review Board at Guangxi Medical University (irb@gxmu.edu.cn).

Response to Requirement 5 (Ethics Statement): The ethics statement has been moved to the Methods section under a dedicated "Ethics Statement" subsection. It has been removed from all other sections.

Responses to Reviewer #1

*Reviewer #1, Comment 1: Although this study uses a longitudinal cohort with repeated quarterly measures, the analysis primarily focuses on trajectory group membership and between-group differences. It is unclear how outcomes (e.g., HIV testing frequency, PrEP/PEP use, sexual behaviors) changed from baseline to follow-up within individuals. The authors should clarify whether and how within-person changes over time were assessed.

Response: We thank the reviewer for this valuable methodological suggestion. We fully agree that assessing within-person changes over time is important in longitudinal studies. However, the main objective of our study was to identify distinct longitudinal trajectories of HIV testing frequency and to examine how these trajectory groups differ in terms of prevention uptake and sexual risk behaviors—rather than to model individual-level change over time per se. We believe the trajectory-based approach (GBTM) is appropriate for this research question, as it captures heterogeneity in testing patterns and allows group-level comparisons using Cox regression, which directly addresses our primary aim.

That said, we acknowledge that we did not explicitly report within-person changes from baseline to end of follow-up. To address this concern without introducing additional statistical models that fall outside our pre-specified analysis plan, we have:

1.Added a limitation statement in the Limitation section acknowledging that we did not apply mixed-effects or GEE models to formally test within-person change, while noting that GBTM inherently captures individual-level longitudinal patterns by grouping participants who follow similar developmental trajectories.

2.Added descriptive comparisons of key outcomes between baseline and follow-up in the Discussion to provide readers with a general sense of observed changes.

(See Limitation in the revised manuscript, lines 27-35, page 10)

*Reviewer #1, Comment 2: *The manuscript reports recruitment between September 2021 and February 2022, with follow-up completed by February 2023, but elsewhere states that follow-up lasted “until March 2022.” These statements are inconsistent.*

Response: We apologize for this inconsistency. We have clarified the study timeline as follows:

Baseline recruitment: September 1, 2021 to February 28, 2022

Follow-up schedule: 3, 6, 9, and 12 months after baseline

Final follow-up completion: February 28, 2023

Maximum follow-up duration: 12 months for all participants

The inconsistent statement has been corrected.

(See Methods in the revised manuscript, lines 10-14, page 4)

*Reviewer #1, Comment 3: *The study period overlaps with COVID-19 control measures in China, which may have affected access to HIV testing and PrEP services.*

Response: We agree with the reviewer. We have added a discussion of this limitation in the Limitation section, noting that while study sites did not experience strict lockdowns during recruitment, local mobility restrictions and temporary clinic closures may have affected access to services. We have explicitly stated that readers should interpret the findings with consideration of this unique pandemic context.

(See Limitations in the revised manuscript, lines 8-14, page 10)

*Reviewer #1, Comment 4: The definitions of “low,” “middle,” and “high” HIV testing frequency are inconsistent between the main text and figure legend. The rationale for the chosen cut-points should be justified.

Response: We thank the reviewer for catching this inconsistency. We have:

1.Harmonized the definitions across the manuscript based on recommendations from multiple international guidelines: the WHO (2019) recommends annual testing for sexually active MSM and 3–6 monthly testing for those at increased risk; the US CDC (2025) recommends annual screening for MSM, with more frequent testing (every 3–6 months) for high-risk individuals; and the IAS-USA (2024) advises 6-monthly HIV testing for PrEP users and 3-monthly testing for frequently exposed individuals.

2.Final definitions: Low (<1 test/3 months), Medium (1–2 tests/3 months), and High (≥3 tests/3 months).

3.Added justification in the Methods section and updated the Figure 1 legend accordingly.

(See Methods in the revised manuscript, lines 3-10, page 5, and Fig 1 legend)

*Reviewer #1, Comment 5: The sample is relatively young and includes a high proportion of students, which may not fully represent the broader MSM population in China.

Response: We agree with the reviewer. We have:

1.Added comparisons with other Chinese MSM cohorts in the Limitations section: a cohort study in Zhuhai reported that MSM aged 18–24 accounted for 23.18%, with students comprising only 6.62%; a 28-province study (N= 2,618 ) reported 26.90% aged <25 years and 18.80% students; and a Northwest China study reported 16.3% aged 18–25 years with <8.1% students.

2.Explicitly stated that these comparisons suggest our sample is significantly younger and more student-dominated than many other Chinese MSM cohorts, limiting generalizability to older MSM and non-student populations.

3.Called for future studies with more diverse age and occupational groups to validate our findings.

(See Limitation in the revised manuscript, lines 15-24, page 10)

*Reviewer #1, Comment 6: The terms “pretreatment” and “post-treatment” visits are unclear in the context of this cohort analysis and may imply an intervention effect.

Response: These terms have been replaced with "baseline" and "follow-up" throughout the manuscript.

(See Methods in the revised manuscript, lines 24-25, page 4)

*Reviewer #1, Comment 7: *The authors may consider discussing digital tools in improving HIV testing, such as doi:10.1001/jamanetworkopen.2025.44821*

Response: We thank the reviewer for this suggestion. We have added a brief discussion on digital tools in improving HIV testing among MSM in the Discussion section, citing the recommended reference (doi:10.1001/jamanetworkopen.2025.44821). We note that integrating such digital approaches into HIV prevention programs in southern China may complement facility-based testing and help address barriers such as stigma and privacy concerns.

(See Discussion in the revised manuscript, lines 1-6, page 9, and Reference 36)

*Reviewer #1, Comment 8: *Table 1 appears to contain potential internal inconsistencies (e.g., reporting zero sexual partners while also reporting a high proportion of HIV-positive partners).*

We thank the reviewer for carefully identifying this issue. We sincerely apologize for this error. Upon re-examination, we found that the inconsistencies in Table 1 were caused by data transcription errors during the preparation of the manuscript. Specifically:

The variable "condomless anal sex with men (past 6 months)" was incorrectly placed: the correct values should be Yes: 182 (55.66%), No: 145 (44.34%). These data were previously assigned to the wrong row.

The variable "positive sex partner in the past 6 months" was also misclassified. The correct values are Yes: 43 (13.15%), No: 230 (70.34%), Uncertain: 54 (16.51%).

We have now carefully verified all data entries in Table 1 against the original dataset and corrected the erroneous row placements. The revised Table 1 has been updated accordingly, and all corrections have been highlighted in the revised manuscript.

To prevent such errors in the future, we have implemented a double-check procedure: all tables will now be independently verified by a second author against the original data before submission.

We sincerely apologize for these oversights and appreciate the reviewer's diligence in catching these issues.

(See Table 1)

Responses to Reviewer #2

*Reviewer #2 (General Comment): Very nicely laid out and written manuscript. Would revise to focus on 'Use of PrEP' among trajectories as primary objective and STI as secondary. The only technical concern is that some of the subgroups trajectories fall below 5% of the study population which may indicate that alternative grouping strategies need to be considered. Conclusion should also reconcile differences between PrEP and PEP uptake.

Response: Thank you for the positive feedback. We have:

1.Refocused the manuscript to present PrEP/PEP use as the primary outcome and STI as secondary, with adjustments made to the Abstract, Introduction, Methods, and Results sections.

2.Addressed the <5% subgroup issue by adding an explanation that although the 4.8% and 4.91% proportions are slightly below the pre-specified 5% threshold, sensitivity analyses with alternative model specifications (2-group and 4-group solutions) confirmed the presence of these distinct trajectory groups. The original 3-group solution was retained because it provided the best fit to the data (lowest BIC) and clinical interpretability.

3.Revised the Conclusion to separately discuss PrEP and PEP: PrEP use was more strongly associated with HIV self-testing, while PEP use was more closely linked to facility-based testing.

(See Introduction in the revised manuscript lines 42-43, page 3, Results lines 3-13, page 8, and Conclusion lines 39-43, page 10)

Reviewer #2 (Abstract Line #17): "men" not "man"

Response: Corrected. "man who have sex with man" has been changed to "men who have sex with men (MSM)" throughout the manuscript.

Reviewer #2 (Introduction): "INTRODUCTION" not "INTRUDITION"

Response: Corrected.

*Reviewer #2 (Introduction Lines 18-19): I believe that authors wanted to state that "retest" rates were less than 20%*

Response: We have clarified this statement: "An Australian study indicated that HIV retest rates among MSM were below 40% after one year and below 20% after six months."

Reviewer #2 (Introduction Line 42 & Methods Line 26): Aim in examining STI incidence is not consistent with abstract.

Response: We have revised these sentences to clarify that PrEP/PEP use is the primary objective and STI incidence is secondary.

(See Introduction in the revised manuscript lines 42-43, page 3, Results lines 3-13, page 8, and Conclusion lines 39-43, page 10)

Reviewer #2 (Statistics Line 8): Please include actual and minimum allowable posterior assignment probability.

Response: We have added: "the minimum acceptable posterior assignment probability for trajectory group membership was set at ≥0.8."

(See Methods in the revised manuscript, lines 17-18, page 5)

Reviewer #2 (Results Line 4 and 11): Please explain why high use of 4.8% and 4.91% were allowed when 5% was minimum.

Response: We have added an explanation in the Statistics section: "Although our pre-specified minimum group size was 5%, the 4.8% and 4.91% proportions represent slight deviations due to model optimization based on BIC. We conducted sensitivity analyses with alternative model specifications (2-group and 4-group solutions), which confirmed the presence of distinct trajectory groups. The original 3-group solution was retained because it provided the best fit to the data (lowest BIC) and clinical interpretability."

(See Methods in the revised manuscript, lines 18-23, page 5)

Reviewer #2: Would reorder Incidence of STI and Use of HIV Exposure Prophylaxis actions.

Response: The Results section has been reordered as suggested: "Use of HIV exposure prophylaxis (PrEP/PEP)" now appears before "Incidence and risk of STI."

(See Results in the revised manuscript, lines 7-13, page 8)

Reviewer #2 (Discussion and Conclusion): Statistics on condom use should be highlighted earlier; age and PEP association should be discussed.

Response: We have:

1.Added condom use descriptive statistics in the baseline characteristics section of the Results.

2.Added a discussion of potential barriers to linking self-testing to PEP for younger MSM: lack of awareness about PEP availability, perceived low risk, cost concerns, and fear of disclosure.

(See Results in the revised manuscript, lines 12-13, page 6, and Discussion lines 1-6, page 9)

Conclusion

We sincerely thank the editor and both reviewers for their time, expertise, and constructive feedback, which have been invaluable in strengthening our manuscript. We have made every effort to address all comments thoroughly and believe that the revised version is substantially improved.

We acknowledge that some of the methodological concerns raised—particularly regarding within-person change analyses—represent important avenues for future research. We are fully open to making additional revisions should the editor or reviewers feel that further improvements are needed. Please do not hesitate to let us know if any aspect of our response or revision requires additional clarification or adjustment; we would be happy to address it promptly.

We appreciate your continued consideration of our work and look forward to your further guidance.

Sincerely,

Ning Chuanyi, MD, PhD

Corresponding author

On behalf of all authors

Attachment

Submitted filename: Response to Reviewers.docx

pone.0358578.s005.docx (22.9KB, docx)

Decision Letter 1

Long Nguyen

8 Jul 2026

Exploring the Relationship Between HIV Testing Frequency and Sexual Behavior, Prevention Prophylaxis Use Among MSM in Southern China

PLOS One

Dear Dr. Ning,

Please see the reviewers' comments and address them carefully.

==============================

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #1: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #3: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #3: Yes

**********

Reviewer #1: Thank you for inviting me to re-review the revised manuscript. All the comments have been addressed.

Reviewer #3: The authors have addressed most of the concerns raised in the previous review, and the manuscript has improved substantially in clarity, organization, and interpretation. The additional discussion on COVID-19, generalizability, digital HIV testing tools, and the rationale for the trajectory groups strengthens the manuscript. The revised analyses and responses are generally satisfactory.

However, several issues remain that should be corrected before the manuscript is accepted. Most are issues of consistency, completeness, and presentation rather than fundamental methodological concerns.

Comments to the Authors

Thank you for carefully revising the manuscript and providing detailed responses to the reviewers. I appreciate the considerable effort made to address the previous comments. I have only a few remaining suggestions.

1. The definitions of low-, middle-, and high-frequency HIV testing remain inconsistent between the Methods section and Figure 1. In the Methods, the categories are defined as low (<1 test/3 months), middle (1–2 tests/3 months), and high (≥3 tests/3 months). However, the Figure 1 legend still defines the middle group as "1 time every 3 months" and the high group as "≥2 times every 3 months." These definitions should be fully harmonized throughout the manuscript.

2. In the response letter, the authors state that descriptive comparisons between baseline and follow-up outcomes were added. However, I could not clearly identify these comparisons in the revised manuscript. Either include the promised descriptive comparison or revise the response letter to accurately reflect the changes that were made.

3. The response letter indicates that discussion was added regarding barriers to PEP uptake among younger MSM (e.g., awareness, perceived risk, cost, disclosure concerns). I was unable to locate this discussion in the revised manuscript. Please either incorporate the promised discussion or modify the response accordingly.

4. The manuscript states that sensitivity analyses using alternative trajectory models (2-group and 4-group solutions) confirmed the selected model and refers readers to Supplementary Table S1. Please ensure that this supplementary table is included in the submission and contains the reported model fit statistics.

Minor inconsistencies and typographical errors

Several editorial issues remain and should be corrected during revision, including:

Figure 1 legend incorrectly describes HIVST as "HIV facility-based testing."

The heading "Use of HIV exposure prophylaxis prophylaxis" contains a duplicated word.

Multiple duplicated punctuation marks (e.g., "..").

Minor spacing and formatting inconsistencies.

The sentence beginning "WHO has HIVST serves as..." is grammatically incorrect and should be rewritten.

The statement "Sequence data have been deposited..." is inappropriate for this study and appears inconsistent with the revised Data Availability Statement. Please replace it with language consistent with the actual data-sharing policy.

Consistency between the response letter and manuscript

A few statements in the response letter describe revisions that are not fully reflected in the manuscript. Before resubmission, I recommend carefully cross-checking the response letter against the revised manuscript to ensure that every promised revision has actually been implemented.

**********

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Reviewer #1: No

Reviewer #3: No

**********

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PLoS One. 2026 Sep 29;21(9):e0358578. doi: 10.1371/journal.pone.0358578.r004

Author response to Decision Letter 2


11 Jul 2026

Manuscript ID: PONE-D-25-58406R1

Title: Exploring the Relationship Between HIV Testing Frequency and Sexual Behavior, Prevention Prophylaxis Use Among MSM in Southern China

Journal: PLOS ONE

Dear Dr. Nguyen and Reviewers,

Thank you very much for giving us the opportunity to revise and resubmit our manuscript to PLOS ONE. We are sincerely grateful to the reviewers for taking the time to carefully evaluate our work. The constructive comments have been invaluable in strengthening our manuscript. We have addressed all concerns point-by-point as detailed below. All changes in the manuscript have been highlighted using track changes.

Responses to Reviewer #3

*Reviewer #3, Comment 1: The definitions of low-, middle-, and high-frequency HIV testing remain inconsistent between the Methods section and Figure 1. In the Methods, the categories are defined as low (<1 test/3 months), middle (1–2 tests/3 months), and high (≥3 tests/3 months). However, the Figure 1 legend still defines the middle group as “1 time every 3 months” and the high group as “≥2 times every 3 months.”

Response: We thank the reviewer for this careful observation. We have now thoroughly harmonized the definitions across the entire manuscript. The final definitions are: Low frequency (<1 test per 3 months), Medium frequency (1–2 tests per 3 months), and High frequency (≥3 tests per 3 months). These definitions have been consistently applied in the Methods section, Results section, Fig 1 (main text and legend). All corresponding text and figure legends have been revised and highlighted in the updated manuscript.

(See Results section: "Definition of Trajectory Groups"; Fig 1 legend and Fig 1)

*Reviewer #3, Comment 2: In the response letter, the authors state that descriptive comparisons between baseline and follow-up outcomes were added. However, I could not clearly identify these comparisons in the revised manuscript.

Response: We thank the reviewer for this comment. In the previous revision, we added descriptive comparisons between baseline and follow-up outcomes in the Discussion section, specifically within the paragraph on descriptive trends. To present these data more clearly, we have also provided the full descriptive comparison table as Supplementary Table S3. This table includes key indicators such as HIV testing frequency (overall, HIVST, and SBHT), PrEP/PEP use, unprotected sexual behavior, and STI cases from baseline to each follow-up time point.

We have noted in both the table and the Discussion that baseline recall periods differ from follow-up: HIV testing reflects the past 12 months at baseline versus the past 3 months at follow-up; unprotected sexual behavior reflects the past 6 months at baseline versus the past 3 months at follow-up; and PrEP/PEP use reflects lifetime use at baseline versus past-3-month use at follow-up. These descriptive data are intended to provide readers with an overview of raw trends and no formal statistical testing was performed.

(See Discussion section, lines 24-34, page 8; Supplementary sTable3)

*Reviewer #3, Comment 3: The response letter indicates that discussion was added regarding barriers to PEP uptake among younger MSM. I was unable to locate this discussion in the revised manuscript.

Response: We thank the reviewer for pointing this out. We apologize for this omission. We have now added a discussion of barriers to PEP uptake among younger MSM in the Discussion section. We note that there is a gap between frequent HIV self-testing among younger MSM and low PEP uptake. Potential barriers include limited awareness of PEP access, perceived low risk despite frequent testing, out-of-pocket cost concerns, and fear of stigma when seeking PEP at clinics. These findings suggest that integrating PEP education into self-testing platforms and establishing rapid referral pathways may help bridge this gap, particularly for younger MSM.

(See Discussion section, lines 11-23, page 10)

*Reviewer #3, Comment 4: The manuscript states that sensitivity analyses using alternative trajectory models confirmed the selected model and refers readers to Supplementary Table S1. Please ensure that this supplementary table is included in the submission.

Response: We confirm that Supplementary Table S1 has been included in the revised submission. This table contains the model fit assessment indicators (BIC, AIC, and posterior assignment probabilities) for all trajectory models. The table is referenced in the Methods section (Statistical Analysis paragraph) and has been uploaded as part of the Supporting Information files.

(See Supplementary sTable1)

*Reviewer #3 (Minor inconsistencies and typographical errors):

Response: We have carefully corrected all editorial issues identified by the reviewer:

Fig 1 legend: Corrected the erroneous description from "(C) HIVST: HIV facility-based testing" to "(C) HIVST: HIV self-testing."

Duplicate words: Corrected "Use of HIV exposure prophylaxis prophylaxis" to "Use of HIV exposure prophylaxis" in the Results section heading.

Duplicate punctuation: Removed all instances of double periods ("..") throughout the manuscript.

Spacing and formatting: Corrected minor spacing and formatting inconsistencies throughout the manuscript.

Grammatical error: Rewrote "The World Health Organization (WHO) has HIVST serves as a strategy..." to "The World Health Organization (WHO) recommends HIVST as a strategy to enhance the accessibility of HT for individuals at elevated risk."

Data Availability Statement: Replaced the inappropriate statement with the correct Data Availability Statement.

*Reviewer #3 (Consistency between the response letter and manuscript):

Response: We sincerely thank the reviewer for this important reminder. We have carefully cross-checked every statement in the response letter against the actual revised manuscript. All promised revisions have been implemented and highlighted in the revised manuscript with track changes.

Journal Requirements

Response to Data Availability Statement: We have updated the Data Availability Statement to comply with PLOS ONE's policy. The revised statement reads:

"The raw data supporting the findings of this study are not publicly available due to the sensitive nature of the information collected (including sexual behavior and HIV status), which could compromise participant privacy. Data requests may be directed to the Institutional Review Board at Guangxi Medical University (gxmuyfyll@163.com), which will review requests for data access in accordance with the ethical approval granted for this study."

(See Methods section, lines 39-43, page 5)

Conclusion

We sincerely thank the editor and reviewers for their valuable time and expert guidance in improving our manuscript. Each comment has been deeply insightful and has contributed significantly to strengthening our work. We have made every effort to address all comments thoroughly and believe that the revised version is substantially improved in both academic rigor and completeness of presentation.

We fully recognize that scholarly writing is an ongoing process. Should the editor or reviewers feel that further improvements are needed, we remain entirely open to making additional revisions. Please do not hesitate to let us know if any aspect of our response or revision requires further clarification or adjustment; we would be happy to address it promptly.

We sincerely appreciate your continued consideration of our work and look forward to your final decision.

Sincerely,

Chuanyi Ning, MD, PhD

Corresponding author

On behalf of all authors

Attachment

Submitted filename: Response to Reviewers 2.docx

pone.0358578.s006.docx (16KB, docx)

Decision Letter 2

Yury Khudyakov

2 Sep 2026

Exploring the Relationship Between HIV Testing Frequency and Sexual Behavior, Prevention Prophylaxis Use Among MSM in Southern China

PONE-D-25-58406R2

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Kind regards,

Yury E Khudyakov, PhD

Academic Editor

PLOS One

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Acceptance letter

Yury Khudyakov

PONE-D-25-58406R2

PLOS One

Dear Dr. Ning,

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Academic Editor

PLOS One

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Table. Model fit assessment indicators for HIV testing and sexual partner/behavior trajectories in MSM.

    (DOCX)

    pone.0358578.s001.docx (23.9KB, docx)
    S2 Table. Trajectory group characteristics of HIV testing patterns among MSM.

    (DOCX)

    pone.0358578.s002.docx (46.1KB, docx)
    S3 Table. Descriptive changes in HT, HIVST, SBHT, PEP/PEP, unprotected sexual behavior from baseline to 12-month follow-up.

    (DOCX)

    pone.0358578.s003.docx (16.8KB, docx)
    Attachment

    Submitted filename: Response to Reviewers.docx

    pone.0358578.s005.docx (22.9KB, docx)
    Attachment

    Submitted filename: Response to Reviewers 2.docx

    pone.0358578.s006.docx (16KB, docx)

    Data Availability Statement

    The raw data supporting the findings of this study are not publicly available due to the sensitive nature of the information collected (including sexual behavior and HIV status), which could compromise participant privacy. Data requests may be directed to the Institutional Review Board at Guangxi Medical University (gxmuyfyll@163.com), which will review requests for data access in accordance with the ethical approval granted for this study.


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