New Research Demonstrates High Prevalence of Sexually Transmitted Disease Trichomonas Vaginalis and Potential of New Molecular Test to Improve Detection
SAN DIEGO, July 13, 2011 /PRNewswire/ — Two new studies presented this week at a leading infectious disease meeting demonstrate that sexually transmitted disease (STD) caused by the parasite Trichomonas vaginalis is more common than previously thought, especially in women over 40, and that a recently cleared molecular test can help improve detection of the often overlooked but potentially serious infection.
“This new research shows that Trichomonas is an important public health issue, especially in women over 40,” said Ingo Chakravarty, Gen-Probe’s vice president and general manager for women’s health. “We believe our APTIMAÂ® Trichomonas assay, which was cleared by the FDA in April for use on the fully automated TIGRISÂ® system, can play an important role in highlighting the prevalence of the STD and intercepting infections before they cause serious complications.”
The two studies were presented at the 19th Biennial Conference of the International Society for Sexually Transmitted Disease Research (ISSTDR), which ended today in Quebec City, Canada.
“Trichomonas is the Rodney Dangerfield of STDs – it gets no respect,” said Kimberle Chapin, MD, professor of pathology and medicine at Brown Medical School in Providence, Rhode Island. “If left untreated, Trichomonas infections can lead to prenatal complications such as premature membrane rupture during pregnancy, pre-term delivery and low birth weight offspring. Trichomonas also has been associated with increased susceptibility to HIV, the virus that causes AIDS, and prolonged infection with the human papillomavirus, which causes cervical cancer. Screening for Trichomonas is important because infections don’t always cause symptoms, yet can be treated easily with antibiotics when detected.”
In the first study presented at the ISSTDR meeting, researchers tested 7,593 women in 21 states with Gen-Probe’s APTIMA Trichomonas assay, which detects the parasite’s unique genetic code. The women were between the ages of 18 and 89 and were scheduled for routine screening for Chlamydia and gonorrhea, the two most common bacterial STDs. The study results were presented by senior study investigator Charlotte Gaydos, MS, DrPH, professor in the division of infectious diseases at the Johns Hopkins University School of Medicine in Baltimore, Maryland.
The overall prevalence of Trichomonas was 8.7% in the study, higher than the rate of Chlamydia (6.7%) and gonorrhea (1.7%) combined. In contrast to the age distribution typically seen with Chlamydia and gonorrhea, Trichomonas was most common in women over 40, as shown here:
Age N Trichomonas + Chlamydia + Gonorrhea + Overall 7,593 8.7% 6.7% 1.7% 18-19 907 8.5% 14.4% 3.3% 20-29 3,972 8.3% 8.0% 2.0% 30-39 1,667 7.9% 2.5% 0.8% 40-49 720 11.3% 1.9% 0.1% > 50 324 13.0% 0.9% 1.2% ---- --- ---- --- ---
In the study, Trichomonas infections were much more common among black women (20.2%) than in whites (5.7%), Hispanics (5.0%) and Asians (3.8%). By geography, trichomonas infections were most common in the Southeast (14.4%), compared to 9.5% in the Southwest and Midwest, and 4.3% in the Northeast.
The second study presented at the ISSTDR meeting was the clinical trial used to gain FDA clearance for Gen-Probe’s APTIMA Trichomonas assay.
In the study, researchers tested 933 women attending nine OB-GYN, adolescent, family planning or sexually transmitted disease clinics in the United States. Approximately 60% of the women reported symptoms commonly associated with Trichomonas infection.
Four specimen types were collected from each woman: physician-collected vaginal swabs, an endocervical swab, a PreservCyt liquid Pap specimen, and urine. Each specimen was tested with the APTIMA Trichomonas assay on the TIGRIS system. The vaginal swab specimens also were tested for Trichomonas using two traditional methods, “wet mount” microscopic examination and culture. The patient was considered positive if the wet mount or culture tests were positive. Study results are shown here:
Specimen Type N Prevalence Sensitivity Urine 735 11.4% 95.2% Vaginal swab 875 12.7% 100.0% Endocervical swab 920 12.4% 100.0% ThinPrep 813 11.4% 100.0%
Specimen Type Specificity PPV NPV % Urine 98.9% 92.0% 99.4% Vaginal swab 99.0% 93.3% 100.0% Endocervical swab 99.4% 95.8% 100.0% ThinPrep 99.6% 96.9% 100.0%
“In this study, the sensitivity of the APTIMA Trichomonas assay was high in all specimens tested, and much higher than that usually reported for wet mount and culture, confirming results seen in smaller, head-to-head studies,” said Jane Schwebke, MD, professor of medicine/infectious diseases at the University of Alabama at Birmingham. “The APTIMA Trichomonas assay showed consistent performance in symptomatic and asymptomatic patients, in adolescent and adult women, and among specimen collection sites. The availability of such a highly accurate, fully automated molecular assay that can be used to test easily obtained female specimens should facilitate large-scale screening for trichomonas.”
About the APTIMA Trichomonas Assay
The APTIMA Trichomonas assay is the first amplified nucleic acid test specifically cleared to detect the most common curable sexually transmitted disease in the United States. The assay may be used to test clinician-collected endocervical or vaginal swabs, urine, and specimens collected in PreservCyt solution from symptomatic or asymptomatic women.
Trichomonas is a sexually transmitted parasite that causes vaginitis, urethritis and cervicitis in women, and more serious complications if left untreated. The US Centers for Disease Control estimate that 7.4 million American men and women are infected with Trichomonas annually.
Screening for Trichomonas is important because the infection often does not cause symptoms. Unfortunately, screening is limited today due in part to the shortfalls of current testing techniques. Most testing currently is done via culture methods, which are slow and less sensitive than molecular tests, or “wet mount,” which requires the microscopic examination of a sample shortly after it is collected and is even less sensitive than culture.
Gen-Probe is a global leader in the development, manufacture and marketing of rapid, accurate and cost-effective molecular diagnostic products and services that are used primarily to diagnose human diseases, screen donated human blood, and ensure transplant compatibility. Gen-Probe is headquartered in San Diego and employs approximately 1,400 people. For more information, go to www.gen-probe.com.
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