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New test approved for trichomonas vaginalis
Trichomoniasis is the most common curable sexually transmitted infection (STI) in young, sexually active women, according to the Centers for Disease Control and Prevention. An estimated 7.4 million new cases occur each year in U.S. women and men.1
Results of a just-published study indicate a test just approved by the Food and Drug Administration (FDA) might be more accurate in identifying infection than currently available methods.2 The study compared the performance of the Aptima transcription-mediated amplification assay against the currently available Affirm assay (Becton, Dickinson and Company, Franklin Lakes, NJ), which is used in obstetric/gynecology practice. The Aptima test is from Gen-Probe of San Diego. The Aptima Trichomonas vaginalis assay received marketing clearance in Europe in 2010.
The Aptima Trichomonas assay uses the same nucleic acid amplification technologies as the Aptima Combo 2 assay, Gen-Probe's chlamydia and gonorrhea test.
To perform the current study, investigators evaluated specimens from 766 patients. Specimens were retrieved consecutively from patients with vaginal complaints and/or with histories suggestive of sexually transmitted infection. Study results indicate the Affirm assay produced false positive and false negative results, while the Aptima assay detected 36% more infected women and yielded a sensitivity of 100% and no false positives.
Investigators also found that trichomonas infection was most prevalent in women ages 36-45 and in women ages 51-60, says Kimberle Chapin, MD, director of the microbiology lab at Rhode Island Hospital in Providence and lead author of the study. "While this was definitely surprising and a new finding in these age groups, this data has now also been substantiated in the FDA clinical trial data involving multiple sites in the United States including Rhode Island Hospital," says Chapin. "In the Rhode Island population with a low prevalence of sexually transmitted infections, we found that Trichomonas vaginalis infection was higher than that of chlamydia and gonorrhea, supporting the need for routine testing for [the infection] and suggesting a different reason for why women may be seeing their physicians with certain gynecologic complaints."
STI not reportedyet
Chapin has been working with Jane Schwebke, MD, professor of medicine at the University of Alabama at Birmingham, and Charlotte Gaydos, DrPH, MPH, MS, professor in the Division of Infectious Diseases, Department of Medicine at the Johns Hopkins University School of Medicine in Baltimore, in bringing more awareness regarding the prevalence of trichomonas vaginalis. The three scientists are scheduled to present on the subject at the upcoming July 2011 meeting of the International Society for Sexually Transmitted Diseases Research in Quebec City, Canada.
"Really, the issue is how do we yet involve another public health infection. How do we screen for it, and how do we treat it?" observes Chapin. Investigators such as Chapin, Schwebke, and Gaydos have called for the infection to be listed as a reportable disease so it receives proper attention.
Chapin offers the following scenario as a reason for increased emphasis on detecting infection: A physician phoned in a request to Chapin for help with a patient with chronic vaginitis. While the patient had been tested for various STIs and treated for vaginitis, she still suffered with symptoms. A test with the new Aptima test proved trichomonas vaginalis positive; the infection had not been detected by other methods.
Reproductive health clinicians know all too well the "revolving door patient" whose infection is incorrectly diagnosed and/or whose partner is asymptomatic and might be reinfecting the patient, says Chapin. These occurrences are similar to what clinicians saw with chlamydia 10 years ago, she notes.
Results of the current study show an increased prevalence of disease in women ages 51 to 60. The fact that the current study shows a prevalence in older women is intriguing to Chapin. "Is it a sociological thing, where they are not likely to get pregnant, not using birth control, and not using barrier contraception, or is it a more physiologic component, where their vaginal milieu is changing and they are more susceptible?" Chapin asks. "Or is it a chronic infection they may have had, but have been getting mistreated for bacterial vaginosis, which is a similar treatment? To be honest, I think that is a big part of the problem."