Risk of coinfection with Chlamydia trachomatis and Neisseria gonorrhoeae in Nova Scotia.

Background: The frequency of Chlamydia trachomatis and Neisseria gonorrhoeae coinfection can vary depending on their individual incidence and prevalence rates.

Objective: To determine the frequency of C trachomatis and N gonorrhoeae coinfections by evaluating the results of testing in 2007 and 2008 to better inform testing and treatment decisions.

Methods: Specimens from the same patient submitted on the same day served as the basis for the present study. The age, sex and the source of the specimen were also linked to the accession number. Infection and coinfection rates were analyzed in both males and females.

Results: Concurrent testing was performed on 41,567 female specimens and 1827 male specimens, of which, 1495 female samples (3.6%) tested positive for C trachomatis infection and 88 (0.2%) tested positive for N gonorrhoeae infections. Only 31 females were coinfected; however, for those between 11 and 25 years of age, 25 of 61 females (40.1%) with N gonorrhoeae infection also tested positive for C trachomatis infection; conversely, 25 of 1248 females (2.0%) with C trachomatis infection also tested positive for N gonorrhoeae infection. For males, 213 (11.7%) tested positive for C trachomatis infection, and 59 (3.2%) tested positive for N gonorrhoeae infection. In 30 males with N gonorrhoeae between 11 and 25 years of age, and 149 males with C trachomatis, eight coinfections were observed (26.7% and 5.3%, respectively). Of those older than 25 years of age, only five of 905 men and six of 19,465 women were coinfected. None of the 10,935 women who were 30 years of age or older had coinfections.

Conclusion: The N gonorrhoeae coinfection rate in males with C trachomatis may justify empirical antimicrobials; however, in females, the proportion of coinfected may not justify empirical treatment for N gonorrhoeae infection when the C trachomatis test is positive and N gonorrhoeae testing has not been performed.