Context.-Adolescents are at highest risk for infection with Chlamydia trachomatis, an important preventable cause of pelvic inflammatory disease and subsequent tubal factor infertility in US women. Current guidelines for delivery of adolescent primary care services recommend yearly chlamydia screening for those adolescent females considered to be at risk.Objectives.-To describe the epidemiology of prevalent and incident chlamydia infection among adolescent females to assess the appropriate interval for chlamydia screening and to define risk factors that would identify adolescent females to target for screening.Design.-Prospective longitudinal study.Patients.-A consecutive sample of 3202 sexually active females 12 through 19 years old making 5360 patient visits over a 33-month period, January 1994 through September 1996.Setting.-Baltimore, Md, family planning, sexually transmitted disease, and school-based clinics.Intervention.-Testing for C trachomatis by polymerase chain reaction. Main Outcome Measures.-Prevalence and incidence of C trachomatis infections; predictors of positive test result for C trachomatis.Results.-Chlamydia infection was found in 771 first visits (24.1%) and 299 repeat visits (13.9%); 933 adolescent females (29.1%) had at least 1 positive test result. Females who were 14 years old had the highest age-specific chlamydia prevalence rate (63 [27.5%] of 229 cases; P=.01). The chlamydia incidence rate was 28.0 cases per 1000 person-months (95% confidence interval, 24.9-31.5 cases). The median time was 7.2 months to a first positive chlamydia test result and 6.3 months to a repeat positive test result among those with repeat visits. Independent predictors of chlamydia infection-reason for clinic visit, clinic type, prior sexually transmitted diseases, multiple or new partners, or inconsistent condom use-failed to identify a subset of adolescent females with the majority of infections.Conclusions.-A high prevalence and incidence of C trachomatis infection were found among adolescent females. We, therefore, recommend screening all sexually active adolescent females for chlamydia infection every 6 months, regardless of symptoms, prior infections, condom use, or multiple partner risks.

Compared with EIA screening, the strategy with the lowest program costs, a screening strategy that combines use of DNA amplification on cervical specimens in women receiving pelvic examinations, and DNA amplification of urine in women with no medical indications necessitating a pelvic examination, prevents the most cases of PID and provides the highest cost savings. With enhanced sensitivity over the other diagnostic assays and with the use of noninvasive specimen collection, DNA amplification assays should be implemented as cost-effective components of a screening program for C. trachomatis.

These results suggest that age-based screening provides the greatest cost savings of the three strategies examined. However, universal screening is desirable in some situations. In general, screening done by using any criteria and a highly sensitive diagnostic assay should be part of any chlamydial prevention and control program or health plan.

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Polymerase chain reaction (PCR) and ligase chain reaction (LCR) were compared for the diagnosis of Chlamydia trachomatis infections by testing urine specimens from 408 high school female students. After therapy, sequential urine specimens were tested to determine persistence of chlamydial DNA in urine. Baseline PCR of cervical specimens was positive in 53 (13.0%) students, and PCR and LCR of urine specimens were positive in 63 (15.4%) and 60 (14.7%), respectively. After discrepant analysis, 64 (15.7%) patients could be confirmed as truly infected. Follow-up urine specimens from 33 infected patients demonstrated that at 1 -3 days after therapy, PCR and LCR were positive for 40% and 73.3%, respectively. Only at 15 days after therapy did all specimens test negative. Urine tests for Chlamydia organisms should not be used as a test of cure within 3 weeks after treatment. Use of urine assays for screening sexually active adolescents has the potential to significantly improve control of chlamydial infections. Joint Committee for Clinical Investigation of Johns Hopkins University were women, PCR is only approved for use with urine from men followed in the conduct of this study. The study was approved by the Institu-[10]. However, research has demonstrated that PCR is highly tional Review Boards of Johns Hopkins University and the Baltimore City Health Department. sensitive (87.8%) and specific (97.6%) when urine specimens Financial support: Region III Chlamydia Program (CDC); Roche Molecular from female subjects are used [16]. Because PCR and LCR Systems (Branchburg, NJ) and Abbott Laboratories (Abbott Park, IL) donated are so exquisitely sensitive and can detect DNA from nonviable test kits.