This study shows that testing of multiple anatomic sites for chlamydia and gonorrhoea based on sexual history is a useful strategy for screening for chlamydia and gonorrhoea in MSM. Our data support previous reports and national guidelines that suggest benefit of testing swabs obtained from oropharynx and anorectum in addition to urethral samples in MSM [4
The prevalence of C. trachomatis
and N. gonorrhoeae
infection of oropharynx and anorectum in our study is in line with data reported by others [7
]. Similar to those studies, we also found that urethral infections only represent a minority of cases and that anorectal infection is more common. In our setting, the prevalence of chlamydia and gonorrhoea more than doubled with testing of multiple anatomic sites compared to obtained tests for urethral infection alone. The majority of C. trachomatis
infections involved a single anatomic site, which was especially the case for anorectal chlamydia, while only a small majority of N. gonorrhoea
infections involved multiple sites. Altogether, our data strongly support the current guidelines that suggest screening anorectum and oropharyngeal samples based on sexual history in addition to urethral tests [4
The prevalence of C. trachomatis
in oropharyngeal samples was 1.5% which was in similar range as reported for a cohort of women reporting fellatio in the same setting [24
]. Although there is sufficient evidence to screen for oropharyngeal gonorrhoea, there is ongoing debate about the relevance of screening for oropharyngeal Chlamydia [25
]. This debate is about the prevalence and transmissibility of oropharyngeal C. trachomatis
infection. The exact risk of transmission of C. trachomatis
from throat to penis in fellatio is unknown, but a recent study suggests this may be quite considerable [29
]. Altogether, in the absence of clear data about risk of transmission, it seems reasonable to include tests for oropharyngeal chlamydia in the routine screening protocol. Oropharyngeal swabs could be tested simultaneously for N. gonorrhoeae
and C. trachomatis
if a nuclear amplification test is used. In that regard, cost-effectiveness analyses are warranted; a possible method to reduce costs would be to combine swabs from different anatomic sites in a single collection tube and to test these samples simultaneously in a single reaction [30
The current protocol of opportunistic screening of anatomic sites based on sexual history has a much better performance than theoretically would have been obtained with a screening strategy based on reported symptoms. The vast majority of C. trachomatis
and N. gonorrhoeae
infections were asymptomatic, regardless of the anatomic site involved. In addition, the positive predictive values of proctitis and pharyngitis are very low. As such, opportunistic screening is superior to symptom-based screening. We used reported sexual exposure as indication for obtaining anatomic site specific tests. This approach is in line with the current guidelines, but the reliability of sexual history in this context is unclear. Some men may not report exposure for reasons of stigma or embarrassment. An Australian study [31
] states that approximately half of the anorectal infections were self-reported, where half were diagnosed by opportunistic screening. Thus an alternative strategy is opportunistic screening of all anatomic sites in all MSM regardless of reported exposure. Considering that the vast majority of our clients reported sexual contact at all three anatomic sites, that MSM can be very outspoken about their sexual practice (e.g
. deny ever engaging in receptive anorectal intercourse), that the expected prevalence of infection at anatomic sites that were not exposed during sexual contact is low, and the physical burden of obtaining tests from patients denying sexual contact at that specific body site, we believe that opportunistic screening of multiple anatomic sites in all MSM is unlikely of additional value to sexual-history based screening protocol. Nevertheless, studies are warranted to confirm this hypothesis.
In this retrospective analysis we found that higher number of sexual partners, history of STI, and HIV seropositive status were risk factors for chlamydia and gonorrhoea infection at any anatomic site. These are known risk factors for STI and markers of high risk sexual behaviour. Risk factors associated with anorectal infection were older age, higher number of sexual partners, and HIV seropositive status. Our results show an increasing prevalence of both anorectal chlamydia and gonorrhoea infections with increasing age. As such, specific attention should be given to preventive measures and anorectal screening in MSM with those characteristics.
This study has several limitations. First, one client can be included in the database with multiple visits related to different consultations due to the set-up and anonymous character of the database. Based on some variables (age, postal code, and ethnicity), we estimate that 90% of the consultations are unique and 10% are multiple visits. These multiple visits may have introduced some bias when calculating risk factors for chlamydia and gonorrhoea at specific anatomical sites, because those are related to risk behaviour. Secondly, the data presented were collected during routine clinical consultations and only information included in the standard questionnaire was captured systematically. For example, the report of pharyngitis was only recorded if the patient complained about a sore throat, but not specifically asked for. As such, more studies are warranted to confirm our findings.