New research focuses on rapid chlamydia test
New research indicates that a rapid test that uses self-collected vaginal swabs may be effective in diagnosing chlamydia.1 With its ability to deliver results in less than 30 minutes, the test, now in development, would give clinicians a same-day diagnostic and screening tool for chlamydial infection.
Clinicians need effective tools to battle chlamydia's spread. Chlamydia trachomatis infection is the most prevalent sexually transmitted bacterial infection worldwide. Common among sexually active young women, undiagnosed and untreated chlamydial infection can result in complications such as pelvic inflammatory disease, ectopic pregnancy, and infertility.2
According to the Centers for Disease Control and Prevention (CDC), 1,030,911 chlamydia diagnoses were reported in 2006 in the United States, up from 976,445 in 2005.3 Under-reporting of the infection is substantial because most people with chlamydia are not aware of their infections and do not seek testing. Women are frequently re-infected if their sex partners are not treated.
Scientists who have developed the test at the University of Cambridge in the UK have formed a spin-out company, Diagnostics for the Real World, to seek marketing approval for it. The company does plan to seek approval for the test to be marketed in the United States, confirms Helen Lee, PhD, head of the research team.
Check the results
The Chlamydia Rapid Test is an immunoassay-based test that detects chlamydial lipopolysaccharide. The published study is an evaluation of the sensitivity, specificity, and predictive values of the rapid test in comparison with polymerase chain reaction and strand displacement amplification assay. A total of 1,349 women, ages 16 to 54, participated in the trial, held at three United Kingdom clinics.
Polymerase chain reaction assay, considered the reference standard for chlamydial testing, tested positive for C. trachomatis in 8.4%, 9.4%, and 6% of specimens evaluated at the three clinics. In comparison, the rapid test had a positive predictive value of 86.7% and a negative predictive value of 98.6%. Comparison with the strand displacement assay demonstrated a sensitivity of 81.6% and specificity of 98.3% for the rapid test.
The Chlamydia Rapid Test is based on a signal amplification system that greatly improves the sensitivity of rapid tests, explains Lee.
"Because of this improved sensitivity, unlike other existing rapid tests, which require the difficult-to-collect cervical swabs, ours is the only one able to use self-collected vaginal swabs," states Lee. "In 1,063 young women surveyed, 99.4% found the instructions easy to understand, and 95.9% felt comfortable collecting their own vaginal swab specimens."
The Chlamydia Rapid Test is about more than speed of treatment for positive clients, says Penny Barber, chief executive of Brook in Birmingham, one of the clinics that participated in the clinical trial.
"All clients, anxious about having chlamydia, benefit from the relief a rapid result gives," says Barber. "For clinics, there is a strong business case for a method that cuts out the logistics and cost of transporting samples, sending results back, and then contacting clients."
The availability of the Chlamydia Rapid Test results within 30 minutes allows for immediate treatment and contact tracing, potentially reducing the risks of persistent infection and onward transmission, say the research scientists. It also could provide a simple and reliable alternative to nucleic acid amplification tests in chlamydia screening programs, they conclude.
The U.S. National Institutes of Health and the Wellcome Trust, a UK-based charity, provided funding for the research. Pivotal to the Wellcome Trust's decision to fund the program was endorsement from health care professionals that a rapid point-of-care test, based on a non-invasive sample, would transform the acceptability of chlamydia screening in the target population, says Richard Seabrook, head of business development of its Technology Transfer Division. Additional evaluation from diagnostic experts, which shows that the technology will deliver the required sensitivity and will be sufficiently robust for a resource-poor setting, led the charity to support the research, says Seabrook.
What is the next step in research for the chlamydia test? Lee says the scientists are moving forward on several fronts. The research team recently was awarded $50,000 for development of the signal amplification system during the 2007 Tech Museum Awards. The international program honors innovators who are applying technology to benefit humanity.
"Having now developed the platform technology of a simple, rapid, and sensitive test format, we will continue to develop tests for the detection of other sexually transmitted diseases such as gonorrhea," Lee states. "Our next product is a duplex test that would simultaneously detect chlamydia and gonorrhea from the same self-collected sample."
- Mahilum-Tapay L, Laitila V, Wawrzyniak JJ, et al. New point of care Chlamydia Rapid Test — bridging the gap between diagnosis and treatment: performance evaluation study. BMJ 2007; doi:10.1136/bmj.39402.463854.AE.
- Paavonen J, Lehtinen M. Chlamydial pelvic inflammatory disease. Hum Reprod Update 1996; 2:519-529.
- Centers for Disease Control and Prevention. Trends in Reportable Sexually Transmitted Diseases in the United States, 2006. National Surveillance Data for Chlamydia, Gonorrhea, and Syphilis. Fact sheet. Accessed at www.cdc.gov.