STD Quarterly: Check your sexually transmitted disease screening: More young adults are at risk for chlamydia 

One in 25 young Americans are infected with chlamydia, research shows

The 18-year-old patient before you, scheduled for an annual exam, is sexually active and admits that condoms are not always used. What is your next move?

If the patient is female, chances are she will be tested for chlamydia, but if the patient is male and asymptomatic, your practice may not include a routine screen for the sexually transmitted disease (STD). New research may have you rethink your approach. In a nationally representative, prospective cohort study of 14,322 young adults ages 18 to 26, more than one in 25 tested positive for Chlamydia trachomatis.1 The prevalence of chlamydial infection was higher than expected, especially among men, investigators note.

While prevalence varied little by age, infection was more common among women (4.74%) than men (3.67%).1 While chlamydial infection was present in all races, it was six times greater in young black adults than in young white adults, figures indicate. Almost 14% of young black women and more than 11% of black men of comparable ages tested positive for the infection.1

Current screening approaches that focus primarily on clinic-based testing of young women are inadequate, says William Miller, MD, PhD, MPH, lead author of the new research and assistant professor of medicine and epidemiology at the University of North Carolina at Chapel Hill.

"These sexually transmitted infections are important causes of morbidity in the U.S.; however, almost all of our information and understanding is based on clinical data," he notes. "This study provided us with the most comprehensive view of these infections in the general population. These infections were undiagnosed and represent a hidden burden of disease in the general population."

What is the impact?

Chlamydia is the most frequently reported bacterial sexually transmitted infection in the United States, according to the Centers for Disease Control and Prevention (CDC).2 In 2002, 834,555 chlamydial infections were reported to CDC from 50 states and the District of Columbia.2

About 75% of infected women and about half of infected men have no symptoms of chlamydial infection. If symptoms do occur, they usually appear within one to three weeks after exposure. Symptoms in women may include abnormal vaginal discharge or painful urination; men may have abnormal penile discharge or painful urination.2 Chlamydial infections also may increase susceptibility to and transmission of HIV in women and men.3

If untreated, chlamydia can spread into the uterus or fallopian tubes and cause pelvic inflammatory disease (PID) in women. Untreated chlamydial infection in men may lead to epididymitis.2 Recent research has linked decreased pregnancy rates in couples where the man had IgG antibodies — a marker of previous or persistent chlamydial infection.4

While there are no conclusive studies showing that men infected with Chlamydia trachomatis are less fertile than uninfected men, such infection is a threat to female fertility.5

"If one in eight women who are exposed to chlamydia gets PID, and by removing the exposure, you are protecting women’s health, and one in eight babies gets pneumonia, and by preventing the pregnant woman from getting chlamydia you protect the baby, there is a clear potential to be cost-effective," says Julius Schachter, PhD, professor of laboratory medicine at the University of California San Francisco. (Editor’s note: Chlamydia is a leading cause of early infant pneumonia.)

Nucleic acid amplification tests, used on urine samples, offer a noninvasive approach to testing. Infection can be easily treated and cured with antibiotics; a single dose of azithromycin or a week of doxycycline, given twice daily, are the most common drug therapies, according to the CDC.2

Routine screening for young women has increased in recent years, thanks to updated practice guidelines issued by major medical organizations. Routine screening for young women younger than 25 is spelled out in recent guidelines issued by the Chicago-based American Medical Association, the Elk Grove Village, IL-based American Academy of Pediatrics, the Washington, DC-based American College of Preventive Medicine, the CDC, and the U.S. Preventive Services Task Force.

Chlamydia screening of sexually active women ages 15-25 now is one of the performance measures included in the Washington, DC-based National Committee for Quality Assurance’s Health Plan Employer Data and Information Set (HEDIS). The measure was added in 2000.

What about men?

Asymptomatic young adult men account for a large reservoir of infection in the general population; however, screening recommendations have largely excluded men, says Miller.

There is no mandate for screening young men, observes Schachter. Previous studies have shown high prevalence of chlamydia in men.6,7

"It’s clear that there are populations, and we need more research as to which populations are deserving of such screening," he says.

Screening men for chlamydia can be an effective intervention to prevent PID compared to screening women, if the prevalence among men to be screened is substantially higher than in women who can be screened, according to recent research presented at the March 2004 National STD Prevention Conference in Philadelphia.8

If young people are to be screened, it is important to provide services that are sensitive to their needs. According to focus groups conducted among young adults, screening programs should provide more information about the effects of chlamydia, availability of urine testing, and offer ease of treatment to motivate more young people to seek testing.9

While the newly published research is welcome, it reinforces the need for more screening and treatment of chlamydia, says Schachter.

"This new report says that nationwide we have a very high prevalence of an infection which we now know how to detect and is easily treatable," he states. "It is an important cause of morbidity, and we should be doing something about it."


1. Miller WC, Ford CA, Morris M, et al. Prevalence of chlamydial and gonococcal infections among young adults in the United States. JAMA 2004; 291:2,229-2,236.

2. Centers for Disease Control and Prevention. Chlamydia. Atlanta; May 2004. Accessed at:

3. Fleming DT, Wasserheit JN. From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection. Sex Transm Infect 1999; 75:3-17.

4. Idahl A, Boman J, Kumlin U, et al. Demonstration of Chlamydia trachomatis IgG antibodies in the male partner of the infertile couple is correlated with a reduced likelihood of achieving pregnancy. Hum Reprod 2004; 19:1,121-1,126.

5. Krause W, Bohring C. Male infertility and genital chlamydial infection: Victim or perpetrator? Andrologia 2003; 35:209-216.

6. Nsuami M, Cohen DA. Participation in a school-based sexually transmitted disease screening program. Sex Transm Dis 2000; 27:473-479.

7. Ku L, St Louis M, Farshy C, et al. Risk behaviors, medical care, and chlamydial infection among young men in the United States. Am J Public Health 2002; 92:1,140-1,143.

8. Gift T, Dunne EF, Chapin J, et al. The cost-effectiveness of screening men for chlamydia to prevent pelvic inflammatory disease (PID) in women. Presented at the 2004 National STD Prevention Conference. Philadelphia; March 2004.

9. Blake DR, Kearney MH, Oakes JM, et al. Improving participation in Chlamydia screening programs: perspectives of high-risk youth. Arch Pediatr Adolesc Med 2003; 157:523-529.