In the early 1980s, expert opinion suggested that Chlamydia trachomatis coexisted with Neisseria gonorrhoeae in up to 45 percent of patients infected with the latter organism. The Centers for Disease Control and Prevention (CDC) recommended that patients diagnosed with gonorrhea infection also be treated for Chlamydia. Although diagnostic testing for C. trachomatis has improved, the most accurate tests are expensive. Because the rate of sexually transmitted diseases (STDs) in the United States has decreased significantly since the early 1980s, the need for co-treatment of these infections has been questioned. Lyss and associates in the Project RESPECT Study Group compared Chlamydia and gonorrhea infection rates in patients treated at STD clinics in five U.S. cities from 1993 to 1995.

Twenty percent of the men and 42 percent of the women infected with N. gonorrhoeae also tested positive for C. trachomatis; many of these patients did not have treatment indications for Chlamydia. These infection rates, along with more recent prevalence data and the low sensitivity of current Chlamydia tests, support the continuation of the CDC's recommendation.

The authors conclude that unless Chlamydia infection has been ruled out by highly sensitive tests, universal co-treatment for patients with gonorrhea remains appropriate.