Gonorrhoea found more frequently in the throat than any other site in gay men

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Gay men should have regular throat swabs to check for infection with gonorrhoea, American investigators emphasise after a study conducted in San Francisco found that 6% of gay men had the sexually transmitted infection in their throat, usually without any symptoms. The study, which is published in the November 15th edition of Clinical Infectious Diseases (now online) also found that the throat was the most common site for gonorrhoea infection in gay men and that younger age and a greater number of oral sex partners were significantly associated with gonorrhoea of the throat.

The US Centers for Disease Control reported that in 2003 the prevalence of gonorrhoea amongst gay men was 15%. Earlier studies looking at the prevalence of pharyngeal gonorrhoea – gonorrhoea of the throat – amongst gay men have found a prevalence of between 3% and 15%. However, there are a lack of longitudinal data from an on-going cohort of gay men looking at the prevalence, incidence and risk factors for gonorrhoea infection in the throat.

Investigators from the EXPLORE study in San Francisco therefore performed gonorrhoea tests on 603 gay men at baseline and then at six-monthly intervals. Swabs were taken from the throat, penis and rectum. The men were also asked to provide demographic information and details of their recent sexual risk behaviour.

Glossary

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

oral sex

Kissing, licking or sucking another person's genitals, i.e. fellatio, cunnilingus, a blow job, giving head.

oral

Refers to the mouth, for example a medicine taken by mouth.

rectum

The last part of the large intestine just above the anus.

multivariate analysis

An extension of multivariable analysis that is used to model two or more outcomes at the same time.

To be included in the study, the men had to be HIV-negative at baseline. The mean age was 36 years, 71% were white, 72% had completed secondary education or higher, and over two-thirds had an annual income of $30,000 or more.

At baseline, 5% had gonorrhoea in the throat, and 18% of individuals had at least one episode of gonorrhoea of the throat during the course of the study. Of the individuals who became HIV-positive during follow-up, 21% had at least one episode of gonorrhoea of the throat.

Overall prevalence of pharyngeal gonorrhoea was 6%, compared to 2% for rectal gonorrhoea and 1% for urethral gonorrhoea. There were 943 person-years of observation available for the investigators’ analysis and they determined that the incidence of gonorrhoea of the throat was eleven per 100 person years, compared to four cases per 100 person years for rectal gonorrhorea and two cases per 100 person years for gonorrhoea infection in the urethra.

In their initial analysis, the investigators found that performing sex on a man known to be HIV-positive, a greater number of oral sex partners and younger age were all significantly associated with gonorrhoea of the throat. However, in multivariate analysis, only younger age (under 44-years, p < 0.05), and performing oral sex on five or more men (p < 0.05) remained significant.

A sore throat was not predictive of pharyngeal gonorrhoea meaning that in most cases gonorrhoea infection in the throat was asymptomatic.

Although gonorrhoea in the throat clears without treatment in 50% of cases within one week and in all cases within three months, the investigators emphasise that the high prevalence of the infection found in their study demonstrates that the throat acts as a “reservoir” for gonorrhoea transmission amongst gay men. They therefore recommend that all sexually active gay men should have a throat swab to check for gonorrhoea in the throat annually, and that gay men who have multiple or anonymous partners should have such swabs every three to six months.

References

Morris SR et al. Prevalence and incidence of pharyngeal gonorrhea in a longitudinal sample of gay men who have sex with men: the EXPLORE study. Clin Infect Dis 43: (online edition), 2006.