Rapid Diagnostic Tests Making Strides in Improving Clinicians Timely Diagnostic Abilities
By Tina Brooks
Rapid diagnostic tests, also called point-of-care tests, are used by the millions. Simplification of these tests in recent years have encouraged their adoption, with test results now available in minutes, or at most an hour or two. Having such immediate results allows for timely diagnosis for appropriate treatment. These tests are particularly advantageous when knowledge of a communicable disease is needed quickly or when patients are apprehensive about a disease and may not return for the results.1
Rapid diagnostic tests are being used in a variety of hospital settings, including laboratories, the ER, labor and delivery, and even the operating room (OR). These tests are not only adding to clinical accuracy, but also to preparedness in dealing with diseases such as influenza and human immunodeficiency virus (HIV).
When these tests first came out, the literature was not there to support them, says Loleta Robinson, MD, director of medical affairs at Thermo Electron Corp. As time moves on, clinicians are starting to realize a need for rapid tests, so youre seeing more articles being published.
Before these tests were available, particularly for influenza, the physician had to make a clinical judgment or an educated guess, says Joshua Ojwang, PhD, associate director of research at ZymeTx, Inc. Many medical conditions exhibit the same type of symptoms as influenza. The symptoms of influenza are so common that flu-like symptoms is a household phrase.
Srikant Iyer, MD, of Cincinnati Childrens Hospital Medical Center, says, If we looked at the number of children discharged from our ER with a diagnosis of influenza three or four years ago, it would be very low. Most of those children would have been diagnosed with either a febrile illness or viral syndrome, not really specifically influenza. Now were able to provide a definitive diagnosis.
Michael Towns, MD, vice president medical affairs at BD Diagnostic Systems, says, The products have performed quite well with adequate sensitivity and good specificity, which allows one to make good therapeutic and infection control decisions.
Of course, this supports the recent efforts to reduce the use of antibiotics. The CDC and other organizations have been saying to everyone to know what youre diagnosing before giving out antibiotics to decrease the resistance that were seeing, Robinson says.
Often, patients present a day or two later with their illness. In order for antivirals to have their greatest efficacy, you would need to do direct rapid testing to be able to determine which patients to give the drugs to, Towns says. Most antivirals need to be administered within 36 to 48 hours of the onset of symptoms.
S. Wayne Kay, president and CEO of Quidel, notes that the market for all influenza testing grew from $9 million in 2000 to $61 million in 2003. This immense growth is a significant measure of our investment in educating the marketplace about what we believe to be better, quicker identification and confirmation of influenza, which probably has most been benefited during that same period of time by the advent of antiviral therapeutics that are now available, he says.
In spite of these great strides in testing, influenza and pneumonia combined remain the seventh leading cause of death among all Americans and the fifth leading cause of death for those over the age of 65.
For influenza to be managed in a way that it will reduce mortality and morbidity, all components of influenza disease management must cooperate with each other, Ojwang says. Of course you have to do vaccination, then diagnosis and those people who are positive should be treated with antiviral drugs. You should also have surveillance to give you the hot spots so that treatment can be concentrated in those areas.
During this past influenza season, Cincinnati Childrens Hospital Medical Center tracked the increasing number of influenza infections seen in the area. Iyer says that they were able to institute the appropriate precautions in his institution because they knew when it was going around.
Since the first case of pediatric HIV infection in 1984, there have been tremendous medical and public health achievements in preventing mother- to-child transmission of HIV.2 When recommended antiretroviral and obstetric interventions are used, expectant mothers have less than a 2 percent chance of delivering an HIV-infected infant as compared to approximately 25 percent without intervention.
In 2002, the Office of the Inspector General (OIG), however, found that one of the significant barriers cited by obstetricians of offering HIV tests were the unavailability of technology to produce timely results. Based on its findings, OIG recommended that the CDC help states develop and implement protocols for HIV testing during labor and delivery as the standard of care.
The law in New York now requires that hospitals provide HIV test results within 12 hours of admission of a woman who is expecting, says William Bruckner, vice president of strategic marketing at OraSure. Previously, hospitals depended upon the traditional lab-based testing for those results, which was 72 hours. Other states are following suit, amending their laws for quicker HIV test results.
In order to meet these new time parameters, several hospitals have begun using rapid diagnostic tests for HIV. Simplicity of these tests does not mean reduction of accuracy, sensitivity and specificity, says Marie McCarthy, MSC, marketing manager at Trinity Biotech. The FDA has been very strong on ensuring with the level of testing demanded of companies like ourselves that we bring into the market tests that are equivalent in performance of existing tests such as ELISA and the Western Blot.
Robert Weinstein, MD, chairman of infectious diseases at Stroeger Hospital of Cook County in Chicago, has been involved in three studies involving the use of rapid diagnostic tests for HIV in different hospital settings.
With regard to the ER, Weinstein and his colleagues find that OraQuick has performed as well as conventional enzyme immunoassay (EIA or ELISA). Weinstein mentions that at least half of the people who test positive dont perceive themselves at a risk for HIV. Whether the test makes a difference or not in patient outcomes when hospitalized is yet to be determined.
Along with Weinsteins team, OraSure is discovering that the ER is an ideal location for routine rapid HIV testing because so many people present in that setting. Its an opportunity to identify HIV-positive people and get them into counseling and treatment much quicker than they normally would, Bruckner says.
Mc Carthy says, Perhaps with the improvement in therapy, HIV testing will gain greater acceptance, so it wont be stigmatized in the way that it is at the moment. Therefore, the use of rapid tests will become more commonplace.
With regard to infection control, Weinstein notes that these tests can be very useful and should be considered for possible incorporation into needlestick protocols. If someone gets stuck with a needle, you want to know whether the source is HIV-positive or not, he says. Send off a conventional test and you dont find out for days. With the rapid test, you can find out right then and there whether the source is HIV positive and whether the person who was stuck should be receiving post-exposure prophylaxis after the needle-stick.