Screening for asymptomatic Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium in medical students in Barcelona

Sir,

Screening programs for asymptomatic sexually transmitted infections (STIs), especially Chlamydia trachomatis (CT), are inconsistent among different countries and their cost-effectiveness is a matter of debate.^[1] Many efforts have been made to target special populations such as university students in the UK and Japan.^[2] No studies are available on asymptomatic STI among Spanish university students. Therefore, we aimed to determine the prevalence of asymptomatic CT, Neisseria gonorrhoeae (NG), and Mycoplasma genitalium (MG) among medical students in the Universitat de Barcelona, Spain.

The protocol was approved by the Hospital Ethics Committee and was conducted in accordance with institutional standards. All study participants gave written informed consent. All medical students were invited to take part anonymously in the study between September 2017 and June 2019. Inclusion criteria were age between 18 and 30 years and being sexually active. Exclusion criteria included antibiotic intake in the previous 4 weeks and symptoms suggesting a possible STI. Anyplex^® CT/NG real-time detection kit (Seegene, CT/NG sensitivity 96%, specificity 99%) was used until September 15, 2018, and multiplex real-time polymerase chain reaction Allplex^® STI Essential Assay Q (Seegene, CT/NG sensitivity and specificity 100%, MG sensitivity 95%, specificity 100%) afterward due to changes in the microbiology department. Therefore, during the 1^st year of the study, only CT and NG tests were performed, and during the 2^nd year of the study, the tests also included MG. First-void urine specimens were collected from men and self-taken vaginal swabs were collected from women. Treatment was given, if necessary, according to the International Union against STIs guidelines.

During the inclusion period, 103 students enrolled in the study (72.8% female and 27.2% male), 31% of targeted population. All individuals were tested for CT and NG, while 55 were also tested for MG (41 females [74.5%] and 14 males [25.5%]). Sociodemographic characteristics and variables are presented in [Table 1]. Four females (3.9% of all participants, 5.3% of women) had positive results (3 CT and 1 MG). No NG infections were detected. Global prevalence of CT and MG was 2.9% (3/103, 95% confidence intervals [CI] 1.0–8.3) and 1.8% (1/55, 95% CI 0.3–9.5), respectively. Considering only women, the prevalence of CT and MG was 4.0% (3/75, 95% CI 1.4–11.1) and 2.4% (1/41, 95% CI 0.4– 12.6). All individuals with positive results reported having stable partners at the time of the study. Their use of condoms was occasional and their perceived risk of STI transmission was low. A positive test for CT was associated with the combination of stable and sporadic SP over the previous 12 months (P = 0.012). No associations with other variables were found. The frequency of positive results was higher in those women who had sought an app-based sexual partner than those who had not (25% vs. 4.8%), but the difference did not reach statistical significance (P = 0.08).

The global prevalence of CT and MG found in this study is lower than the recent prevalence reported in individuals between 16 and 25 years.^[3] However the prevalence observed among female students was comparable to the CT and MG prevalence documented among asymptomatic women in the area. Therefore, the medical knowledge of the students did not imply a lower risk of STI acquisition.

All participants with positive results had stable SP and their perception of STI risk was low. Having both sporadic and stable partners in the previous year was the only risk factor associated with CT infection. This fact highlights the importance of screening based on several risk factors, rather than only the number of SP or perceived risk. Men who have sex with men (MSM) are also a well-known risk factor for STI. However, we found no positive results in MSM students. Another finding to point out is the disparity between those undergoing cervical cytology and STI screening. Almost 70% of female students reported that they had had cervical cytology testing as against 6.8% who had undertaken opportunistic STI testing previously. The Spanish Ministry of Health consensus and other organizations recommend STI testing based on risk assessment.^[4] Only 6.8% of study participants undergoing STI screening previously indicates that more efforts are needed in this direction.

Relatively small sample size and not collecting rectal and pharyngeal swabs from MSM were the major limitations.