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National Institute of Allergy and
Infectious Diseases (NIAID)

Wednesday, May 22, 1996
6:00 p.m. Eastern Time

Media Contact:
John Bowersox
(301) 402-1663

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Chlamydia Screening May Reduce Pelvic Inflammatory Disease Rates

Routine screening for a common cervical infection could significantly reduce women's risk for pelvic inflammatory disease (PID), a study supported by the National Institute of Allergy and Infectious Diseases (NIAID) suggests.

Researchers at the University of Washington and Group Health Cooperative of Puget Sound, both in Seattle, found that women who were screened and treated for asymptomatic chlamydial infections were nearly 60 percent less likely than unscreened women to develop PID, an infection of the upper reproductive tract that often leads to infertility, tubal pregnancy and other serious complications. The finding is reported in the May 23 issue of The New England Journal of Medicine.

"This finding holds great promise for improving the health of young women," said Department of Health and Human Services Secretary Donna E. Shalala. "The findings should also remind all of us that regular health screening is the foundation of good health."

PID affects more than 1 million women in the United States each year. Most cases are caused by Chlamydia trachomatis, the most common sexually transmitted bacterial pathogen in the United States. According to the Centers for Disease Control and Prevention (CDC), more than 4 million people each year are diagnosed with chlamydia. Experts say the actual number of cases probably is much higher, since chlamydial infections often produce no symptoms and thus frequently go undiagnosed. Research reviewed at a recent NIAID workshop on PID suggests that up to 40 percent of untreated chlamydial infections in women ascend the upper genital tract to cause PID. Scientists have hypothesized that identifying and treating women with asymptomatic chlamydial infections could reduce the burden of PID.

"This is an extremely important finding that potentially could have an enormous impact on a very costly disease," says NIAID Director Anthony S. Fauci, M.D. Dr. Fauci notes that studies have estimated the costs associated with treating PID and its consequences at between $5 billion and $7 billion each year.

In an editorial accompanying the paper, CDC officials praised the result as a "landmark" finding. "Screening for chlamydia should become the standard of care for young, sexually active women," says the CDC's Judith N. Wasserheit, M.D., M.P.H., one of the editorial's authors. The CDC has spearheaded an effort to establish a nationwide chlamydia prevention program.

A prior study of women enrolled in a health maintenance organization (HMO) had shown that certain characteristics, such as being younger than 25 years, unmarried, and having two or more sex partners during the previous year, were associated with a higher than average risk for chlamydia infection. Using these and other criteria, researchers Delia Scholes, Ph.D., Walter E. Stamm, M.D., and their colleagues identified a study population of approximately 2,600 women who were assigned at random to either an intervention or control group.

Throughout the study, women in both groups continued to receive all necessary medical care from their HMO physicians. In addition, women in the intervention group were screened for chlamydial infection and those who tested positive were treated with antibiotics. Women in the control group who presented with symptoms of cervical inflammation were tested for chlamydial infection, then treated.

One year later, follow-up questionnaires and reviews of the participants' medical records revealed that nine cases of PID had occurred among the 1,009 women in the screening group, compared with 33 cases of PID among the 1,598 women who were treated when symptomatic. From these data, the incidence of PID--the rate at which new cases occur during a specific period--was calculated to be 56 percent lower in the screened group as compared with the control group.

"We've provided the most direct evidence to date that early detection and treatment of asymptomatic chlamydial infections can reduce the incidence of PID, at least among certain populations of young women," says Dr. Stamm, the study's principal investigator.

Penelope Hitchcock, D.V.M., chief of NIAID's Sexually Transmitted Diseases Branch, notes that the study represents a significant advance in the Institute's PID research program.

"These results tell us that we can intervene early, during lower genital tract infection, and make a difference by preventing many cases of PID," she says. The finding also underscores the importance of developing better diagnostic tests for STDs. Until recently, she says, difficulties associated with diagnosing asymptomatic chlamydial infection precluded widespread screening. However, since the current study was begun, a non-invasive, urine-based assay developed by Abbott Laboratories working with NIAID investigators allows earlier detection of both asymptomatic and symptomatic cases of chlamydia infection, says Dr. Hitchcock. NIAID researchers currently are trying to develop even faster, less expensive assays for chlamydia and other sexually transmitted pathogens.

Despite the improved prospects for PID prevention, Dr. Hitchcock adds that another critically important issue--finding better ways to diagnose and treat women with asymptomatic PID--remains a formidable research challenge.

"As many as 25 percent of all women of reproductive age have already had an episode of PID, and most of them were undiagnosed and untreated," she says. "Research toward identifying women with subclinical PID could ultimately help prevent many cases of ectopic pregnancy, infertility and other serious consequences of this disease."

In addition to Dr. Scholes and Dr. Stamm, co-authors include Andy Stergachis, Ph.D., Fred E. Heidrich, M.D., M.P.H., Holly Andrilla, M.S., and NIAID grantee King K. Holmes, M.D., Ph.D.

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 May 22, 1996