To the Editor—We read with great interest the report by Evers et al [1], exploring the anatomical site distribution and risk factors for pharyngeal Chlamydia trachomatis infections in a large sample of men who have sex with men (MSM) in The Netherlands. The investigators reported a 10.6% prevalence of C. trachomatis overall, but a low prevalence of pharyngeal infections (1.2%). Compared with rectal and urogenital sites, pharyngeal C. trachomatis infections comprised the lowest prevalence by anatomic site.
We would like to share findings of an ongoing study screening for C. trachomatis and Neisseria gonorrhoeae among MSM enrolled in a human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP) program in Hanoi, Vietnam. PrEP has been available in Vietnam since 2019 [2]. The Sexual Health Promotion Clinic is the largest PrEP program in Hanoi, providing PrEP for 2695 individuals cumulatively [3]. Our study provides quarterly screening for C. trachomatis and N. gonorrhoeae at 3 anatomic sites using nucleic acid amplification testing, as recommended by the Vietnam national PrEP guidelines [4].
Thus far, 218 study participants have enrolled; all are MSM with a median age of 24.0 years (interquartile range: 21.5–28.0 years) (Table 1). Overall, the prevalence of C. trachomatis at any anatomic site was 23% (50/218), with rectal infections comprising 68% (34/50) and urogenital infections comprising 20% (10/50). Chlamydia trachomatis was detected in 6.9% (15/218) of pharyngeal specimens. The prevalence of pharyngeal-only C. trachomatis was 4.1% (9/218). Pharyngeal and rectal infections occurred concurrently in 12% (6/50), but there were no concurrent pharyngeal and urogenital infections. The prevalence of pharyngeal C. trachomatis was 9.1% (5/55) among those reporting pharyngeal symptoms in the past week compared with 6.1% (10/163; P = .45) among those without.
Table 1.
Demographic, Behavioral, and Clinical Characteristics of 218 Men Who Have Sex With Men in an HIV PrEP Program in Hanoi, Vietnam
| Chlamydia trachomatis Infections | ||||
|---|---|---|---|---|
| All Participants (N = 218) | Overall (n = 50) | Pharyngeal (n = 15) | Pharyngeal-Only (n = 9) | |
| Median [IQR] age, years | 24.0 [21.5–28.0] | 24.0 [21.5–28.0] | 23.9 [20.9–29.1] | 23.9 [20.9–29.1] |
| Age | ||||
| 16–24 years | 117 (53.7) | 24 (48.0) | 6 (40) | 2 (22.2) |
| 25–34 years | 85 (39) | 20 (40.0) | 5 (33.3) | 4 (44.4) |
| ≥35 years | 16 (7.3) | 6 (12.0) | 4 (26.7) | 3 (33.3) |
| Number of male partners in the past month, median [IQR] | 1 [1–2] | 2 [1–3] | 2 [1–3] | 2 [1–2] |
| Oral sex in the past week | 124 (56.9) | 36 (72.0) | 11 (73.3) | 6 (66.7) |
| Deep kissing in the past week | 119 (54.6) | 32 (64.0) | 11 (73.3) | 6 (66.7) |
| Pharyngeal symptoms in the past week | 55 (25.2) | 13 (26.0) | 5 (33.3) | 3 (33.3) |
| Genital symptoms in the past week | 35 (16.1) | 6 (12.0) | 1 (6.7) | 0 (0) |
| Rectal symptoms in the past week | 33 (15.1) | 8 (16.0) | 4 (26.7) | 1 (11.1) |
| Genital C. trachomatis | 10 (6.9) | 10 (20.0) | 0 (0) | 0 (0) |
| Rectal C. trachomatis | 34 (15.6) | 34 (68.0) | 6 (40.0) | 0 (0) |
| Pharyngeal C. trachomatis | 15 (6.7) | 15 (30.0) | 15 (100) | 9 (100) |
Data are presented as n (%) unless otherwise indicated. Abbreviations: HIV, human immunodeficiency virus; IQR, interquartile range; PrEP, pre-exposure prophylaxis.
The prevalence of both pharyngeal and pharyngeal-only C. trachomatis infections within our study population of MSM on PrEP in Vietnam was higher than the Evers et al estimates among MSM in The Netherlands. Similar to the findings here, we recently reported a C. trachomatis prevalence of 28.5% overall, 6.3% for pharyngeal and 5.2% for pharyngeal-only C. trachomatis, among HIV-uninfected MSM in Hanoi [5]. Evers et al report pharyngeal and pharyngeal-only C. trachomatis infections were the lowest prevalence sites, but we found a higher prevalence of pharyngeal infections compared with urogenital infections. We also found most pharyngeal infections were asymptomatic. The differences in prevalence are likely explained by the different study populations and settings, but access to screening might play a role, as most of our study population was receiving screening for the first time.
Screening for pharyngeal C. trachomatis for MSM on PrEP continues to be recommended by many national guidelines [6, 7]. However, as Evers et al note, spontaneous clearance of infections, infrequent symptoms, and rare development of complications limit the individual and public health impact of screening. Additionally, there are costs to screening, which are particularly important in resource-limited settings, and potential harms to overtreatment such as adverse effects and increased antimicrobial resistance due to more antibiotic consumption [8]. Additional research on clinical outcomes and cost-effectiveness is needed to demonstrate the clinical and public health benefit of pharyngeal screening for C. trachomatis.
Contributor Information
Hao T M Bui, Center for Training and Research on Substance Abuse–HIV (CREATA-H), Hanoi Medical University, Hanoi, Vietnam.
Paul C Adamson, Division of Infectious Diseases, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
Giang M Le, Center for Training and Research on Substance Abuse–HIV (CREATA-H), Hanoi Medical University, Hanoi, Vietnam.
Jeffrey D Klausner, Population and Public Health Sciences, Keck School of Medicine at USC, Los Angeles, California, USA.
Notes
Ethics statement. The study was approved by the Institutional Review Board of Hanoi Medical University.
Financial support. This work was supported by the US National Institute of Allergy and Infectious Diseases (R21 AI157817 to G. M. L and J. D. K.) and the Fogarty International Center (K01TW012170 to P. C. A). All authors report a no charge donation of study materials from Abbott Molecular.
References
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