Between 1997 and 1998, undiagnosed gonorrhea and chlamydia infections occurred in a combined one in 12, or 7.9 percent, of young adults ages 18 to 35 in Baltimore, a surprisingly high total that approaches or exceeds the number of such infections that were diagnosed and treated there in 1998, researchers found.
Such sexually transmitted diseases, which can cause pain, infertility and death in some cases by promoting transmission of the AIDS virus, may be significantly more prevalent than previously believed, at least in some U.S. areas and populations, the scientists said.
A report on the findings appears in the Feb. 13 issue of the Journal of the American Medical Association. Authors represent the Research Triangle Institute, the University of North Carolina at Chapel Hill and Johns Hopkins University.
"We used powerful new DNA-amplification tests that can detect minute quantities of bacteria," said Dr. Charles F. Turner, a principal scientist at RTI and lead author. "The bacteria do not need to be alive or plentiful.
Thus, it is possible that we are detecting the residue of old untreated infections that are no longer transmissible or clinically significant. Our suspicion is strengthened by the fact that only 2 to 5 percent of infected subjects reported having symptoms during the past six months."
Three percent of the entire sample had untreated chlamydia, and more than 5 percent showed untreated gonorrhea, said Turner, who also is an applied social research professor at the City University of New York. He and his colleagues believe, but have not confirmed, that the new tests allowed them to look back in time and observe infections that were contracted months or years ago and never effectively treated.
"Clearly, a better job needs to be done in finding and treating such infections," he said.
Co-authors of the paper include Drs. Susan M. Rogers, Heather G. Miller and James R. Chromy of RTI and Drs. William C. Miller and Peter A. Leone of the UNC schools of medicine and public health. Others are computer expert Phillip C. Cooley of RTI and Drs. Thomas C. Quinn and Jonathan M. Zenilman of Hopkins.
Researchers interviewed 728 young adults from a randomly selected cross section of Baltimore households and tested urine specimens from 579, Turner said. Analysis of results from urine specimens subjected to nucleic acid amplification and comparisons with clinically diagnosed cases of gonorrhea and chlamydia showed the high percentages of hidden cases.
UNC's Miller and Leone chiefly helped with data analysis and interpretation of the results and showed possible "false positive" test results were unlikely to have altered the group's findings.
"There appears to be a large reservoir of asymptomatic, untreated infections," Miller said. "This reservoir could be infections with longer duration, which raises questions about their clinical significance and possibly their transmissibility."
"The high prevalence rate in the general public and the lack of symptoms suggests that screening programs and extending access to care are critical for reducing the prevalence of these infections," Leone said.
Since teens pick up infections from adults and pass them on to others, they should be included in subsequent comparable studies, Turner said. The research and parallel studies being conducted by other investigators provide a new model for studying the epidemiology of sexually transmitted diseases using population surveys. They allow estimates of the prevalence of asymptomatic and untreated infections in the entire population and various subgroups.
In an accompanying editorial, Dr. J. Dennis Fortenberry of Indiana University said "veils" surrounding sexually transmitted diseases are not simply those of inadequate documentation of how prevalent the diseases are.
"Societal willingness to stigmatize sexuality and STDs continues to hide issues that are central aspects of our lives," he wrote. "Given the morbidity and costs of STDs, including those due to human immunodeficiency virus infection (HIV, the virus that causes AIDS), these are veils that no longer seem affordable."
Embarrassment among patients and clinicians when discussing sexual health is common, but that is not a good reason for avoiding health risk assessments, Fortenberry wrote.