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Alarmingly High Level of Undiagnosed STDs Found

In Baltimore, the number may exceed that of treated cases

TUESDAY, Feb. 12, 2002 (HealthDayNews) -- A surprising new survey of young adults in Baltimore has found that the number of undiagnosed and untreated cases of chlamydia and gonorrhea each year may actually exceed the number that are diagnosed and treated.

This means that the overall number of cases of these sexually transmitted diseases (STDs) could be at least twice what experts had thought.

The report, appearing in the Feb. 13 issue of the Journal of the American Medical Association, found that one in 12, or 7.9 percent, of individuals between the ages of 18 and 35 in Baltimore has undiagnosed and untreated chlamydia or gonorrhea and that most have no symptoms.

Although it's not possible to generalize the findings beyond the Baltimore area, the results are nevertheless troubling.

"It's hard to say how representative this is for other parts of the country, because this has never been done in any other city," says Susan Newcomer, a statistician and demographer at the National Institutes of Health (NIH). "Just for the citizens of Baltimore, it's a little alarming."

In 2000, 703,093 cases of chlamydia and 358,995 cases of gonorrhea were reported from around the nation to the Centers for Disease Control and Prevention (CDC). Left untreated, infection with either bacterium can result in chronic pelvic pain, infertility, and potentially fatal tubal pregnancy among women. Individuals with chlamydia or gonorrhea are also at greater risk of contracting human immunodeficiency virus (HIV).

To better understand the prevalence of STDs, the researchers interviewed 728 adults between the ages of 18 and 45 and asked them to fill out surveys on sexual behavior, prior STD history, STD symptoms, drug and alcohol use, and social attitudes and behaviors. Within this sample group, 579 respondents aged 18 to 35 provided a urine sample, which was then tested with a NAAT (nucleic acid amplification test), called ligase chain reaction assay.

NAATs are relatively new and simple tests, replacing the older, more invasive method of swabbing. The ease of this new technology is one of the main reasons a study like this one is possible.

The urine test results showed that about 5.3 percent of Baltimore's population between the ages of 18 and 35 have an untreated gonococcal infection, and an estimated 3 percent have an untreated chlamydial infection. About 0.4 percent of adults were estimated to have both infections.

One of the most surprising findings was the high incidence of these STDs among black women: 15 percent with gonorrhea or chlamydia, or both.

"I was surprised by these numbers," says Gerald Stokes, associate professor of microbiology and tropical medicine at George Washington University Medical Center in Washington, D.C. "I thought the numbers would be equal across the board for males and females. I did not expect to see the black female population sticking up." The reasons for the spike aren't clear.

By contrast, black men had a prevalence of 6.4 percent, nonblack men 2.8 percent, and nonblack women 1.3 percent.

Another surprising finding was the difference in diagnosed and undiagnosed gonococcal (gonorrhea-causing) infections among women. The number of women aged 18 to 35 with gonorrhea was widely believed to hover around 1.4 percent to 2.3 percent. This study, however, found that 6.7 percent had an undiagnosed infection.

There was also an unexpectedly high prevalence (10.2 percent) of gonococcal infections among the 31-to-35-year age bracket.

This last finding as well as the other findings may have been affected by the tremendous sensitivity of the NAAT test.

"It is possible that we are detecting the residue of old untreated infections, which are no longer transmissible or clinically significant," says the study's lead author, Charles Turner, a scientist at the Research Triangle Institute in Washington, D.C., and a professor at the City University of New York. "This would not reduce the public health significance of our findings. It would mean that in past year a relatively large number of people may have contracted active infections that were transmissible and risked serious clinical consequences at that time."

Not surprisingly, most of the participants with undetected infections had not experienced symptoms. Only 2 percent reported having burning sensation while urinating, and 4.7 percent reported discharge within the past six months. In the case of chlamydia, this is not so unusual, with the CDC reporting that approximately 75 percent of women and 50 percent of men have no symptoms. For both gonorrhea and chlamydia, women are more likely to be asymptomatic.

Regardless, the study has serious implications in the realm of public health. "We believe routine screening for gonorrhea and chlamydia should be considered whenever young adults and sexually active adolescents come into contact with the health care system," says Susan Rogers, another of the study's authors and also a scientist at Research Triangle Institute.

What to Do: For more information on prevention and treatment of sexually transmitted diseases, visit the Centers for Disease Control and Prevention's STD Prevention site or the American Social Health Association.

SOURCES: Interviews with Susan Newcomer, Ph.D., statistician and demographer, National Institutes of Health, Bethesda, Md.; Charles Turner, Ph.D., scientist, Research Triangle Institute, Washington, D.C. and professor, applied social research, City University of New York; Susan Rogers, Ph.D., scientist, Research Triangle Institute, Washington, D.C.; Gerald Stokes, Ph.D., associate professor, microbiology and tropical medicine, George Washington University Medical Center, Washington, D.C.; Feb. 13, 2002, Journal of the American Medical Association
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