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Chlamydia Widespread in U.S., Task Force Recommends Screening for Young Women


Chlamydia -- the most commonly reported sexually transmitted infection in the U.S. -- had an overall prevalence of 1.7% among people age 14 to 39 in the latest NHANES survey, but this rose to 4.7% among sexually active young women. Updated guidelines from the U.S. Preventive Services Task Force recommend regular chlamydia and gonorrhea screening for sexually active women age 24 and younger, and for older women at increased risk for infection, but state that there is not enough evidence to make a similar recommendation for men.

The burden of chlamydia is likely underestimated because infection is usually asymptomatic and it often goes undetected. Left untreated, chlamydia can lead to pelvic inflammatory disease and infertility.

As described in the September 26 edition of Morbidity and Mortality Weekly Report, Elizabeth Torrone from the Centers for Disease Control and Prevention (CDC) and colleagues analyzed data from the 2007-2012 National Health and Nutrition Examination Surveys (NHANES), looking at chlamydia prevalence according to age, sex, race/ethnicity, and other demographic and behavioral factors.

Based on a sample of 8330 survey participants in the 14-39 year age range who completed questionnaires and gave urine samples for testing, overall chlamydia prevalence was 1.7%, or approximately 1.8 million total infections. However, prevalence rates differed substantially by sex: 2.0% for women vs 1.4% for men.

Looking at women and men combined, rates were 2.4% for people age 14-19 years, 2.9 for those age 20-24, and 1.1 for those age 25-39. Turning to race/ethnicity, for women and men of all ages combined, rates were 5.2% for black participants, 2.3% for Mexican-Americans, and 0.8% for white participants. Combining these factors, young black women had the highest rate, at 13.5%.

Not surprisingly, people with more sex partners and people who started having sex at a younger age were at greater risk. But even among people who reported having only 1 sex partner in the past year, chlamydia prevalence was 1.4%, rising to 1.8% among the small number of respondents who reported no partners during that period. Women who used oral or injectable hormonal contraceptives were no more likely to have chlamydia than those who did not (1.9% vs 2.3%).

"High chlamydia prevalence among sexually active young females in the United States supports screening of all sexually active young females annually so that infected persons can be diagnosed and they and their sex partners can be treated promptly," the report authors concluded.

Clinical Guidelines

The U.S. Preventive Services Task Force (USPSTF) reviewed evidence on screening for chlamydia and gonorrhea in asymptomatic people from studies published since its last review, which it combined with evidence from previous recommendations and reviews.

As set forth in the September 23 Annals of Internal Medicine, the updated guidelines are as follows:

  • The USPSTF recommends screening for chlamydia in sexually active females aged 24 years or younger and in older women who are at increased risk for infection.
  • The USPSTF recommends screening for gonorrhea in sexually active females aged 24 years or younger and in older women who are at increased risk for infection.
  • The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for chlamydia and gonorrhea in men.

The USPSTF found "convincing evidence that screening tests can accurately detect chlamydia and gonorrhea." The task force further found adequate evidence that screening reduces complications of chlamydia in women who are at increased risk, as well as evidence that gonorrhea screening results in a "moderate magnitude of benefit based on the large proportion of cases that are asymptomatic, the effectiveness of antibiotic treatment to reduce infections, and the high morbidity associated with untreated infections."

However, the USPSTF found "inadequate evidence of the benefit of screening for chlamydia and gonorrhea in men, although the harms from screening are small to none."

"In the absence of studies on screening intervals, a reasonable approach would be to screen patients whose sexual history reveals new or persistent risk factors since the last negative test result," the recommendations state.

For people who test positive for chlamydia or gonorrhea, the task force recommends post-test counseling to address safe sex practices that can reduce disease transmission or reinfection, and added that motivational interviewing may help promote risk-reducing behaviors.

To maximize adherence, the CDC recommends that treatment be dispensed on site at the time test results are given. The agency also recommends that all sex partners during the past 60 days of people who test positive for chlamydia or gonorrhea should be evaluated, tested, and treated if needed. For partners who cannot be linked to care, the CDC suggests expedited partner therapy, which allows the person testing positive to also receive drugs for a partner.

Due to a high likelihood of reinfection -- which can occur when partners who have not completed treatment pass an infection back-and-forth between them -- the CDC recommends retesting all patients with chlamydia or gonorrhea at 3 months after treatment.



E Torrone, J Papp, and H Weinstock. Prevalence of Chlamydia trachomatis Genital Infection Among Persons Aged 14-39 Years -- United States, 2007-2012. Morbidity and Mortality Weekly Report63(38):834-838. September 26, 2014.

ML LeFevre on behalf of the U.S. Preventive Services Task Force. Screening for Chlamydia and Gonorrhea: U.S. Preventive Services Task Force Recommendation Statement. Annals of Internal Medicine. September 23, 2014 (Epub ahead of print).