Regular Chlamydia screening recommended

Sexually active teenage girls should be screened for Chlamydia trachomatis infection every six months, not every 12 months as recommended, according to a study by US researchers published in JAMA (1998;280:521-6). High rates of infection and re-infection put young girls at risk of pelvic inflammatory disease, infertility, and ectopic pregnancy.

The study's leader, Dr Gale Burstein, a paediatric and adolescent medicine specialist at Johns Hopkins University in Baltimore, Maryland, said: “I saw so much chlamydia in the clinic. Traditional risk factors didn't explain it. Being an adolescent was the major risk factor.”

The study was conducted in a poor population, with 98% black Americans, in inner city Baltimore, which has high rates of sexually transmitted disease. More than 3200 sexually active girls aged 12 to 19 were screened during more than 5300 visits to family planning, sexually transmitted disease, and school clinics over 33 months. Their mean age was 16.9 years. Girls who had a pelvic examination were screened with a cervical swab. Girls who attended for another reason, such as a sore throat, were screened with a urine test.

Chlamydial infection--almost always asymptomatic--was found in 24% of first visits and 14% of repeat visits. The highest rate, 27.5%, was among 14 year olds. Overall, 29.1% of the girls had at least one positive test result.

Dr Burstein's team recommended testing every six months because most teenagers became infected or reinfected in about six months. Infections were treated with either doxycycline or azithromycin.

“This study has wide relevance,” said Dr Donald Orr, professor of paediatrics at Indiana University School of Medicine in Indianapolis. Rates of sexually transmitted diseases vary nationally, but until recently Indiana had rates similar to inner city Baltimore. Younger girls are at greater risk of infection because of the immaturity of the cervix and immunological naivety. “Screening adolescent boys is just as important as screening girls,” Dr Orr said. “Male partners often won't believe they're infected and don't get treated.”