The high number of cases of chlamydia found among adolescent girls has prompted health experts to recommend screening all sexually active adolescent girls for chlamydia infection every six months, according to an article in the August 12 issue of The Journal of the American Medical Association (JAMA).

Gale R. Burstein, M.D., of Johns Hopkins University in Baltimore, and colleagues studied 3,202 sexually active girls aged 12 to 19 years over 33 months to determine the incidence and prevalence of chlamydia trachomatis (CT) infection, a sexually transmitted disease (STD). The girls were screened for chlamydia infection during 5,360 visits to family planning, STD and school-based clinics in the Baltimore area.

The authors write: “The results of our study elucidate the need for universal chlamydia screening of all sexually active adolescent females, regardless of symptoms. Most of the infections identified were asymptomatic. Complaint of STD symptoms was not an independent predictor of chlamydia infection and only identified 23 percent of infections.”

The authors recommend changing current annual screening guidelines to once every six months because their study indicates that the median time between an initial negative test result and a subsequent positive test result was 7.2 months, and 25 percent of the positive results occurred within five months.

During the study period, the researchers found that 20 percent of all chlamydia tests performed on adolescent girls were positive. Chlamydia infection was found in 24.1 percent of first clinic visits and 13.9 percent of repeat visits. Overall, 29.1 percent of girls in the study had at least one positive test. Fourteen-year-olds had the highest proportion of positive chlamydia tests (27.5 percent).

CT infection is the most important preventable cause of pelvic inflammatory disease (PID) and subsequent tubal factor infertility in women in the United States, according to information cited in the study. Chlamydial PID often has few or no symptoms, so screening programs play an important role in the prevention of infertility.

The researchers report that independent behavioral and clinical predictors of chlamydia (i.e., being seen in an STD clinic, having multiple or new sex partners or inconsistent condom use) failed to identify a high-risk subset of adolescent girls with the majority of infections. Also, none of the variables could be used to identify a large proportion of the chlamydia infections among the adolescent girls in this study without performing chlamydia screening at almost every clinic visit.

They conclude: “This study, like others, confirms that risk factors, including behavioral, fail to identify a high risk subgroup of adolescent females to target for chlamydia screening. Chlamydia control programs have succeeded by screening all sexually active adolescent females, regardless of sexual practices or demographics. Public health researchers should concentrate future efforts on prevention and partner notification rather than continuing to categorize adolescent females at risk.”