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Point-of-care tests eyed in stemming rise in STDs
Search is on for accurate, efficient tests to reduce transmission
What is your facility's protocol when it comes to testing for sexually transmitted diseases (STDs)? It probably involves patient testing, with treatment provided after test results are completed. What happens, though, if tests results aren't available at the time of the initial patient visit? Some patients might never return for results and subsequently will miss out on needed care.
It's time to change the rules when it comes to testing: Five of the top 10 reportable diseases in the United States are STDs.1 The burden of disease is greatest in young people. Statistics estimate that one in two sexually active people will contract an STD by the time they turn 25.2 Are clinicians stepping up their game when it comes to STD testing? A 2002 national survey indicates "no" less than one-third of U.S. physicians said they routinely screen for such infections.3
Point-of-care (POC) testing allows clinicians to provide immediate and confidential test results and treatment, state authors of a new review of current STD tests.4 The tests also provide a teachable moment so clinicians can provide immediate patient feedback that might impact their risk behaviors. For these reasons, POC tests may be of great importance for the care of adolescents and young adults, the authors state.4 Effective communication of results can increase patient understanding and compliance with risk reduction strategies, which might affect the STD epidemic.5
In looking at a test's characteristics, clinicians look at sensitivity (the proportion of infected people who have a positive test) and specificity (the proportion of uninfected people who have a negative test). While point-of-care tests might be less sensitive than other lab tests, when return rates are below a certain rate, a less sensitive test with immediate treatment might treat more cases.6
How can clinicians evaluate point-of-care tests when it comes to STD detection? Authors of the current review of POC tests developed a scoring system based on the ASSURED criteria set forth by the World Health Organization's STI Diagnostics Initiative. ASSURED is an acronym for STI diagnostics that meet specific criteria:
Look at HIV tests
Clinicians might be most familiar with rapid tests for HIV. A survey conducted by the National Alliance of State and Territorial AIDS Directors shows that 94% of health departments use rapid HIV testing in conjunction with health department-supported HIV testing programs.7 Certain tests are Clinical Laboratory Improvements Amendments (CLIA) waived, which categorizes them as simple tests.
The following rapid HIV tests are approved by the Food and Drug Administration (FDA) and are CLIA waived on the medium named:
Chembio Diagnostics, a New York-based company that develops, manufactures, licenses, and markets proprietary rapid diagnostic tests, developed the technology behind the Clearview HIV tests, which are marketed by Inverness Medical. The company is developing has developed a rapid oral fluid HIV test, says Larry Siebert, Chembio president. The test is based on the company's patented Dual Path Platform technology. The trial is under way in the United States, he confirms.
Chembio also is testing a unique combination screen and confirm point-of-care test for syphilis. At the current time, no rapid test is available in the United States [POC chlamydia tests are available in Europe] for detecting the STD.
Public health officials are zeroing in syphilis. Data released at the 2010 National STD Prevention Conference shows the rate of primary and secondary syphilis among men who have sex with men (MSM) is more than 46 times that of other men and more than 71 times that of women.9 The new analysis reports the range as 91-173 cases per 100,000 MSM versus two per 100,000 other men and one per 100,000 women.9
Chembio is working with the CDC in developing the Dual Path Platform Syphilis Screen and Confirm test, says Siebert. The test is designed to detect both of the markers that together offer an indication of a confirmed case of active untreated syphilis. The company has identified U.S. clinical sites for study of the test and forecasts study initiation at the end of the second quarter of 2010, says Siebert.
How about chlamydia?
Screening with nucleic acid amplification tests is recommended to decrease levels of chlamydia infection in young women; however, such tests are costly and time-consuming.
The FDA has approved three rapid tests for detecting chlamydia infection: the BioStar optical immunoassay (no longer available), Clearview Chlamydia (Inverness Medical), and QuickVue (Quidel, San Diego, CA).4 In the current review, the three tests are listed as moderately complex to perform and demonstrate sensitivity rates of 25%-65% compared with nucleic acid amplification tests.4
One rapid test that might hold promise is the Chlamydia Rapid Test, developed by scientists at Diagnostics for the Real World and the University of Cambridge, both in Cambridge England. The test, a urine-based screening tool that can be used with minimal training, is available in Europe, but not in the United States.
Researchers are examining other chlamydia rapid tests. Preliminary research on two potential tests indicate disappointing sensitivities for both devices for cervical and vaginal samples.10 Specificity of one device was poor but was very good for the other, researchers report. A larger sample size might provide more reliable estimates of test performance in high and low risk women, they conclude.10
There are other tests in the pipeline which are significantly promising, says Charlotte Gaydos, MS, MPH, DrPH, professor of medicine in the Division of Infectious Diseases at Johns Hopkins University (JHU) and principal investigator of the Center for Point-of-Care Tests for Sexually Transmitted Diseases funded by the National Institute of Biomedical Imaging and Bioengineering. One such test involves a microwave-accelerated, metal–enhanced, fluorescence-based assay. It is being developed by the Center for Point-of-Care Tests for Sexually Transmitted Diseases, says Gaydos. Other tests in the pipeline include cartridge based amplification tests, which are simple to perform and should have much higher sensitivity than available tests, says Gaydos.
"Trials for these products are currently under way," says Gaydos. "Future months show exciting progress for POC diagnostics for sexually transmitted infections."