Infection Control Today - 05/2004: OR Topics

Rapid Diagnostic Tests Making Strides in Improving Clinicians Timely Diagnostic Abilities

By Tina Brooks

Rapid diagnostic tests, also calledpoint-of-care tests, are used by the millions. Simplification of these tests inrecent years have encouraged their adoption, with test results now available inminutes, or at most an hour or two. Having such immediate results allows fortimely diagnosis for appropriate treatment. These tests are particularlyadvantageous when knowledge of a communicable disease is needed quickly or whenpatients are apprehensive about a disease and may not return for theresults.¹

Rapid diagnostic tests are being used in a variety of hospitalsettings, including laboratories, the ER, labor and delivery, and even theoperating room (OR). These tests are not only adding to clinical accuracy, butalso to preparedness in dealing with diseases such as influenza and humanimmunodeficiency virus (HIV).

When these tests first came out, the literature was notthere to support them, says Loleta Robinson, MD, director of medical affairsat Thermo Electron Corp. As time moves on, clinicians are starting to realizea need for rapid tests, so youre seeing more articles being published.

Influenza

Before these tests were available, particularly forinfluenza, 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 symptomsas influenza. The symptoms of influenza are so common that flu-likesymptoms is a household phrase.

Srikant Iyer, MD, of Cincinnati Childrens Hospital MedicalCenter, says, If we looked at the number of children discharged from our ERwith 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 illnessor viral syndrome, not really specifically influenza. Now were able toprovide a definitive diagnosis.

Michael Towns, MD, vice president medical affairs at BDDiagnostic Systems, says, The products have performed quite well withadequate sensitivity and good specificity, which allows one to make goodtherapeutic and infection control decisions.

Of course, this supports the recent efforts to reduce the useof antibiotics. The CDC and other organizations have been saying toeveryone to know what youre diagnosing before giving out antibiotics todecrease 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 dodirect rapid testing to be able to determine which patients to give the drugsto, Towns says. Most antivirals need to be administered within 36 to 48 hoursof the onset of symptoms.

S. Wayne Kay, president and CEO of Quidel, notes that themarket for all influenza testing grew from $9 million in 2000 to $61 million in2003. This immense growth is a significant measure of our investment ineducating the marketplace about what we believe to be better, quickeridentification and confirmation of influenza, which probably has most beenbenefited during that same period of time by the advent of antiviraltherapeutics that are now available, he says.

In spite of these great strides in testing, influenza andpneumonia combined remain the seventh leading cause of death among all Americansand the fifth leading cause of death for those over the age of 65.

For influenza to be managed in a way that it will reducemortality and morbidity, all components of influenza disease management mustcooperate with each other, Ojwang says. Of course you have to dovaccination, then diagnosis and those people who are positive should be treatedwith antiviral drugs. You should also have surveillance to give you the hotspots so that treatment can be concentrated in those areas.

During this past influenza season, Cincinnati ChildrensHospital Medical Center tracked the increasing number of influenza infectionsseen in the area. Iyer says that they were able to institute the appropriateprecautions in his institution because they knew when it was going around.

HIV

Since the first case of pediatric HIV infection in 1984, therehave been tremendous medical and public health achievements in preventingmother- to-child transmission of HIV.2 When recommended antiretroviral andobstetric interventions are used, expectant mothers have less than a 2 percentchance of delivering an HIV-infected infant as compared to approximately 25percent without intervention.

In 2002, the Office of the Inspector General (OIG), however,found that one of the significant barriers cited by obstetricians of offeringHIV tests were the unavailability of technology to produce timely results. Based on its findings, OIG recommended that the CDC helpstates develop and implement protocols for HIV testing during labor and deliveryas the standard of care.

The law in New York now requires that hospitals provide HIVtest results within 12 hours of admission of a woman who is expecting, saysWilliam Bruckner, vice president of strategic marketing at OraSure. Previously, hospitals depended upon the traditionallab-based testing for those results, which was 72 hours. Other states arefollowing suit, amending their laws for quicker HIV test results.

In order to meet these new time parameters, several hospitalshave begun using rapid diagnostic tests for HIV. Simplicity of these testsdoes not mean reduction of accuracy, sensitivity and specificity, says MarieMcCarthy, MSC, marketing manager at Trinity Biotech. The FDA has been verystrong on ensuring with the level of testing demanded of companies likeourselves that we bring into the market tests that are equivalent inperformance of existing tests such as ELISA and the Western Blot.

Robert Weinstein, MD, chairman of infectious diseases atStroeger Hospital of Cook County in Chicago, has been involved in three studiesinvolving the use of rapid diagnostic tests for HIV in different hospitalsettings.

With regard to the ER, Weinstein and his colleagues find thatOraQuick has performed as well as conventional enzyme immunoassay (EIA orELISA). Weinstein mentions that at least half of the people who test positivedont perceive themselves at a risk for HIV. Whether the test makes adifference or not in patient outcomes when hospitalized is yet to be determined.

Along with Weinsteins team, OraSure is discovering that theER is an ideal location for routine rapid HIV testing because so many peoplepresent in that setting. Its an opportunity to identify HIV-positivepeople and get them into counseling and treatment much quicker than theynormally would, Bruckner says.

Mc Carthy says, Perhaps with the improvement in therapy,HIV testing will gain greater acceptance, so it wont be stigmatized in theway that it is at the moment. Therefore, the use of rapid tests will become morecommonplace.

With regard to infection control, Weinstein notes that thesetests can be very useful and should be considered for possible incorporationinto needlestick protocols. If someone gets stuck with a needle, you want toknow whether the source is HIV-positive or not, he says. Send off aconventional test and you dont find out for days. With the rapid test, youcan find out right then and there whether the source is HIV positive and whetherthe person who was stuck should be receiving post-exposure prophylaxis after theneedle-stick.