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Am Fam Physician. 2007;75(1):110-111

Background: Current guidelines from the Centers for Disease Control and Prevention (CDC) recommend retesting female patients for sexually transmitted infections (STIs) three months after treatment for Chlamydia trachomatis infection because up to 15 percent will acquire new STIs within this time period. The diagnostic yield of retesting male and female patients who present with other STIs is unclear.

The Study: Peterman and colleagues examined data from a randomized controlled trial of human immunodeficiency virus (HIV) prevention counseling (the RESPECT-2 trial) to estimate the incidence of new STIs during the year following an infection.

The study population consisted of 2,419 sexually active patients (1,236 female and 1,183 male) who were 15 to 39 years of age and visited one of three urban STI clinics. Patients were excluded from the analysis if they were HIV positive or denied having vaginal or anal sex in the previous three months. Men who reported having sex with men and patients who missed at least two consecutive follow-up visits also were excluded.

Eligible patients underwent urine nucleic acid amplification testing for chlamydia and gonorrhea. Female patients also had vaginal samples cultured for Trichomonas vaginalis. Overall, 265 female (21.4 percent) and 205 male (17.3 percent) patients were diagnosed with at least one STI at the baseline visit. Patients were instructed to return to the clinics at 13-week intervals for one year; STI testing was repeated at each follow-up visit. Multivariate analyses were performed to identify demographic or behavioral factors that were associated with a new STI.

Results: In the end, 319 female and 174 male patients were diagnosed with at least one new STI during the follow-up period; 66.2 percent of these patients reported no symptoms. T. vaginalis was the most common infection in famales (12.8 percent), whereas C. trachomatis was the most common in males (9.4 percent). Female patients 25 years or younger were more likely to become infected with C. trachomatis or Neisseria gonorrhoeae than older women (26 to 39 years of age). A history of a new sexual partner or more than one partner was associated with an increased risk of new infection. Patients who had an STI at the baseline visit were at greatest risk of new infection; 19.6 percent of females and 16.1 percent of males were diagnosed with a new STI within three months.

Conclusion: The authors conclude that patients with C. trachomatis, N. gonorrhoeae, or T. vaginalis infections are at higher risk of acquiring a new STI in the year following the initial diagnosis. Because nearly two thirds of infections were asymptomatic, they further conclude that patients treated for STIs should be instructed to return for rescreening in three months. They caution that the incidence of recurrent infections in this study's high-risk population may not be representative of that in other clinical settings.

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