Sexual health screens which include only urethral tests would miss the majority of cases of Chlamydia and gonorrhoea in gay men, according to a study conducted in San Francisco and published in the July 1st edition of Clinical Infectious Diseases. Clinics offering sexual health services should provide gay men with “straightforward, non-judgmental risk assessments” and appropriate screens for sexually transmitted infections, argue the investigators.
To prevent HIV-infection and transmission, the United States Centers For Disease Control and Prevention (CDC) currently recommend that sexually active gay men should have an annual urethral and urine screen for gonorrhoea and Chlamydia. In addition, men who have had oral sex are recommended to have throat swab to test for gonorrhoea, and men who have had receptive anal sex are recommended to have rectal swabs taken for Chlamydia and gonorrhoea. These tests are recommended regardless of condoms being used or not. Men with multiple partners are recommended to undergo more frequent screening, every three to six months.
However, there is some evidence that few sexual health clinics and gay men’s health centres are offering rectal Chlamydia screening or rectal or throat swabs for gonorrhoea without symptoms of the infection.
Investigators from San Francisco wished to obtain “more data on the prevalence of Chlamydia and gonorrhoea among [gay] men by anatomic site” to encourage “appropriate screening strategies.”
Therefore demographic and clinic data from gay men attending two sexual health clinics in San Francisco were examined from 2003. The investigators had four specific aims:
- To identify the prevalence of oral, throat and rectal infection with Chlamydia and gonorrhoea.
- To determine the proportion of asymptomatic infections.
- To see if men had infections in single or multiple sites.
- To see how many Chlamydia infections would be missed if men were not routinely tested for the infection.
A total of 5539 men attending the municipal sexual health clinic and 895 who used the gay men’s health centre were included in the investigators’ analysis. Approximately 60% of men had rectal swabs taken to check for infection with Chlamydia and gonorrhoea, 85% had throat swabs, and 96% of men attending the municipal clinic were tested for urethral infections, against 88% of men who were patients at the gay men’s health centre.
The anatomical site with the highest prevalence of Chlamydia was the rectum (9% municipal clinic, 6% gay men’s clinic) followed by the urethra (6% municipal clinic, 3% gay men’s clinic) and throat (1% municipal clinic, 2% gay men’s clinic). Gonorrhoea followed a different clinic with the anatomical site with the highest prevalence being the throat (9% municipal clinic, 8% gay men’s clinic), followed by the rectum (8% municipal clinic, 3% gay men’s clinic) and urethra (7% municipal clinic, 2% gay men’s clinic).
Of the 290 men with rectal Chlamydia attending the municipal clinic (there were not enough data to allow for analysis of results from the gay men’s clinic), 57% were HIV-negative or did not know their HIV status. Similarly, of the 139 men with rectal gonorrhoea 57% were HIV-negative or did not know their HIV status.
The majority of cases (85%) of rectal Chlamydia and gonorrhoea at both clinics were asymptomatic. By contrast, only 42% of urethral Chlamydia infections and 10% of urethral gonorrhoea infections were without symptoms.
Just over half (54%) of the men with Chlamydia had the infection in the rectum alone, with 10% of men having the infection in more than more anatomical site. The investigators note “if only urethral screening for Chlamydia was conducted in this population of men who had receptive anal sex during the previous six months, 90% of rectal Chlamydia infections would be missed.”
With regards to gonorrhoea, 36% of men with the infection had it in their throat only, with 28% having the infection in more than one site. Once again, the investigators caution, “if only urethral screening for gonorrhoea was performed, 77% of rectal gonorrhoea infections would be missed.”
The investigators add, “on the basis of our data, the majority of Chlamydial (53%) and gonococcal (64%) infections would be missed if only urine/urethral screening was performed for men who have sex with men.”
In addition, the investigators established that 70% of Chlamydia infections would have been missed if men were only tested for gonorrhoea. A total of 23% of men with rectal gonorrhoea had rectal infection with Chlamydia, 11% of men with gonorrhoea in their urethra also had Chlamydia present in this site, and 4% of men with gonorrhoea in the throat also had Chlamydia in their throat.
The investigators comment, “given that 55% of men with rectal Chlamydial and gonococcal infection reported that they were HIV-negative in our study, it is critical that rectal infections be identified and treated to reduce the risk for acquisition of HIV-infection.”
Providing appropriate sexual health screens for gay men requires that clinicians perform a risk assessment. The investigators recommend guidelines available here for performing non-judgmental risk assessments.
Kent CK et al. Prevalence of rectal, urethral, and pharyngeal Chlamydia and gonorrhea detected in 2 clinical settings among men who have sex with men: San Francisco, California, 2003. Clin Infect Dis 41 (on-line edition), 2005.