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National Institute of Allergy and
Infectious Diseases (NIAID)

Tuesday, Feb. 17, 1998

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Age-Based Screening is Cost-Effective Method to Control Chlamydial Infection

Screening all women younger than 30 years of age may be the most cost-effective method of stopping or limiting chlamydial infections and their consequences according to an article in the February 15 issue of Annals of Internal Medicine.

Investigators from the National Institute of Allergy and Infectious Diseases (NIAID) and Johns Hopkins University compared three strategies to screen 7,699 women without symptoms who attended two family planning clinics in Baltimore, Md. In addition to the age-based screening found to be most effective, investigators evaluated universal screening and screening with the criteria recommended by the Centers for Disease Control and Prevention (CDC). All women were tested with polymerase chain reaction (PCR). They calculated the cost-effectiveness of chlamydial screening by comparing total costs, including screening program costs, and estimating future medical costs of all sequelae.

"Certainly one of the great values of this study," says Anthony S. Fauci, M.D., director of NIAID, "is the confirmation that screening enables clinicians to identify and treat women with chlamydial infections and no symptoms, thus preventing many occurrences of serious sequelae, such as infertility."

Chlamydial infection is one of the leading sexually transmitted diseases in the United States today. The CDC estimates that more than 4 million new cases occur each year. Pelvic inflammatory disease, a serious complication of chlamydial infection, has emerged as a major cause of infertility among women of childbearing age. Genital chlamydial infection is caused by the bacterium, Chlamydia trachomatis, and is transmitted during vaginal or anal sexual contact with an infected partner. A pregnant woman may pass the infection to her newborn during delivery, with subsequent neonatal eye infection or pneumonia. The annual cost of chlamydial infections and their sequelae in the United States exceeds $2.7 billion.

"The majority of women infected with Chlamydia do not have symptoms, and damage to their fallopian tubes resulting in infertility can occur silently over time if the infection remains undiagnosed and not treated," said author Thomas C. Quinn, M.D., of NIAID and Johns Hopkins University, Baltimore, Md. "In our study, 6.6 percent of women attending the Baltimore family planning clinics were found to be infected. Because of the initial lack of symptoms and signs, most of these women would not have been diagnosed or treated if they had not undergone routine screening for Chlamydia using either urine or cervical specimens. New and simple tests make screening easier."

Currently, the CDC recommends testing all women with evidence of an inflamed cervix and all women younger than 20 years of age. They also suggest: (1) testing women 20 to 23 years of age who have not consistently used barrier contraception or have had a new sex partner or more than one sex partner during the past 90 days; and (2) testing women 24 years of age or older who have not consistently used barrier contraception and have had a new sex partner or more than one sex partner during the past 90 days.

The investigators compared each screening strategy’s ability to identify women at risk and thus trigger testing and treatment, which in turn would result in fewer or no sequelae and reduced overall medical costs. They defined medical outcomes as prevented cases of pelvic inflammatory disease, chronic pelvic pain, ectopic pregnancy, infertility, male urethritis and epididymitis in adults, and conjunctivitis and pneumonia in infants.

The results were dramatic. Without screening, there would have been 152 cases of pelvic inflammatory disease and other sequelae in women, men and infants with an associated cost of $676,000. Screening according to CDC criteria would have prevented 64 cases of pelvic inflammatory disease and saved $231,000. Screening all women younger than 30 years of age would have prevented 85 cases of pelvic inflammatory disease and saved $305,000. Universal screening would have prevented an additional six cases, but would have cost considerably more than age-based screening -- approximately $3,000 more per case of pelvic inflammatory disease prevented.

The authors caution that although the study results suggest that age-based screening provides the greatest cost savings, universal screening is desirable is some situations. In general, screening with any criteria and a highly sensitive diagnostic test should be part of any chlamydial prevention and control program. NIAID has a major commitment to develop new sexually transmitted disease (STD) diagnostic tests that are rapid, inexpensive, easy-to-use and do not require an invasive sample. If such tests were available and acceptable to the patient, screening for "silent" STDs would be even more cost-effective.

Authors, in addition to Dr. Quinn, are M. Rene Howell, M.A., and Charlotte A. Gaydos, Dr.P.H., both of the Division of Infectious Diseases at Johns Hopkins University in Baltimore, Md.

NIAID conducts and supports research—at NIH, throughout the United States, and worldwide—to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at

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NIAID Archive

Important note: Information on this page was accurate at the time of publication. This page is no longer being updated.

Last Updated February 17, 1998