Use age to target chlamydial screening

Lack of symptoms means missed infections

Using age as the primary factor in screening women for chlamydial infection may be the most cost-effective method for halting the damaging effects of the sexually transmitted disease (STD).

Chlamydia is one of the leading STDs in the United States. The Centers for Disease Control and Prevention in Atlanta estimates more than 4 million new cases occur each year. If left untreated, chlamydial infection can lead to pelvic inflammatory disease (PID), a major cause of infertility in women of childbearing age.

The problem with chlamydial infection is that for almost all women, and many men, the disease causes no symptoms, says Penelope Hitchcock, DVM, MS, chief of the STD branch of the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health in Bethesda, MD.

"In diseases where you don't have symptoms, if you don't look for the people and you don't screen them, then you don't find them," she notes. Age-based screening "allows us to find people early and do effective therapy."

Investigators from Johns Hopkins University in Baltimore and NIAID compared three strategies in screening 7,699 women without symptoms of chlamydia in two Baltimore family planning clinics.1 The strategies included universal screening, checking all women younger than 30, and using CDC screening guidelines.

The CDC specifications recommend testing all women with evidence of inflamed cervix and all women under age 20. The CDC suggests testing for women in the age 20-23 bracket if they meet one of the risk criteria (inconsistent use of barrier methods or having a new or multiple partners in the last 90 days). Testing for women age 24 and up is suggested if they meet both risk criteria.

Polymerase chain reaction assays were used to test for signs of chlamydial infection. Researchers calculated the cost-effectiveness of the screening by comparing total costs and estimating future medical charges for all sequelae in women, men, and infants. These conditions were included since untreated chlamydia can lead to urethritis and epididymitis in men, conjunctivitis and pneumonia in infants, and PID, chronic pelvic pain, ectopic pregnancy, and infertility in women.

Screening saves dollars

Analysis shows that without screening, there would have been 152 cases of PID and other sequelae in women, men, and infants with an associated cost of $676,000. Screening using CDC guidelines would have prevented 64 cases of PID and saved $231,000. Screening all women under 30 proved to be the most cost-effective: It prevented 85 cases of PID and saved $305,000. While universal screening would have prevented six more cases than age-based testing, it would have added an additional $3,000 per case of prevented PID.

Communities need to assess the prevalence of chlamydia in their areas before determining the most cost-effective method, says Thomas Quinn, MD, professor of medicine at Johns Hopkins and one of the researchers involved in the study.

"Each city or each locality needs to do what we did to determine what the most effective method of screening would be," he suggests. "In this particular scenario, our age cutoff for this population was 30."

The argument was made to keep the age cutoff at 25, since more money was expended to screen those between 25 and 30, Quinn says. Because the prevalence of infection in that age group remained significant in Baltimore, the cutoff age was maintained at age 30. A similar study shows age is among the most important guides providers in family planning and STD clinics can use in testing women for chlamydia.2 Testing all women under 25 was found to detect most infections among those at low risk for contracting STDs based on their sexual behavior and number of partners, the study reveals.

History not effective

Providers can't depend on patient histories alone to determine whether patients are at increased risk for chlamydia, Quinn asserts. "It doesn't fit the pattern like gonorrhea or syphilis does. You should ask background questions, but if you base your screening criteria on history, it will not be very reliable, and you will miss a lot of positive infections."

A study of nearly 9,000 women in four New York City family planning clinics evaluated the reliability of eight self-reported risk factors as a means to identify women with chlamydia. Results showed that testing women for chlamydia only if they reported risk factors did not detect a sufficiently high number of infections.3

With finite resources, public and private payers are taking a hard look at what screening criteria are the most cost-effective in detecting chlamydia, Quinn says. Many facilities are moving toward more sensitive - and more expensive - diagnostic assay tests, so the screening criteria play an important part in determining the cost ratio.

"When [payers] look at the equation, it is, 'Do I spend $10 for one test, or do I spend $5 per test and screen twice as many people?'" he observes. "Given the same amount of money, which way will pick up the most infections and prevent PID? The ultimate goal is to try to prevent the development of PID."


1. Howell MR, Quinn TC, Gaydos CA. Screening for Chlamydia trachomatis in asymptomatic women attending family planning clinics: A cost-effectiveness analysis of three strategies. Ann Intern Med 1998; 128:277-284.

2. Marrazzo JM, Fine D, Celum CL, et al. Selective screening for chlamydial infection in women: a comparison of three sets of criteria. Fam Plann Perspect 1997; 29:158-162.

3. Han Y, Coles FB, Hipp S. Screening criteria for Chlamydia trachomatis in family planning clinics: accounting for prevalence and clients' characteristics. Fam Plann Perspect 1997; 29:163-166.