Researchers Identify a More Definitive Test for a Common STI

A study from the microbiology lab at Rhode Island Hospital has found that a new test may be more accurate in identifying a common sexually transmitted infection (STI), Trichamonos vaginalis (TV). The researchers also noted a high prevalence of TV in women in the 36- to 45- year-old age group -- a group not normally included in the recommended STI screening criteria. The study is now published online in advance of print in the Journal of Clinical Microbiology.

TV is a STI that can affect both men and women, and its symptoms can be associated with many different conditions. Its true prevalence and clinical impact is unknown because current methods of detection exhibit poor sensitivity when compared to molecular amplification methods.

The lead author of the study, Kimberle Chapin, MD, director of the microbiology lab at Rhode Island Hospital, says, "Despite a worldwide prevalence rate likely to be double that of gonorrhea or chlamydia combined, TV is not currently a reportable disease in the United States."

The authors tested the effectiveness of the only Food and Drug Administration (FDA) cleared diagnostic test for differentiating and identifying the pathogens associated with bacterial vaginitis compared with another test that uses a special type of amplification for the detection of TV, known as the APTIMA assay. Clinical trials of the assay were recently completed and it has been submitted to the FDA for clearance.

The authors studied the specimens from 766 women. Through their study, they found that the AFFIRM assay, which is commonly used in OB/GYN patients, produced both false positive and false negative results, while the APTIMA assay detected 36 percent more TV-infected women yielding a sensitivity of 100 percent and no false positives.

Chapin says, "We also found that TV was most prevalent in women ages 36 to 45 and in women ages 51 to 60. 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 US including Rhode Island Hospital. 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 TV and suggesting a different reason for why women may be seeing their physicians with certain gynecologic complaints."