CEO SUMMARY: Respiratory viruses are responsible for 75% of all visits to physicians and yet physicians struggle to identify whether an infection is viral or bacterial. Now there is a new molecular assay with FDA clearance that allows physicians to test for 12 common viral infections. It is the xTAG Respiratory Viral Panel (RVP) from Luminex Molecular Diagnostics. Beaumont Hospital in Royal Oak, Michigan, is one of the first hospitals to offer this test.
MULTIPLEX TESTING IS POISED to make another advance in clinical care. This time it’s a non-invasive, multi-analyte test designed to detect 12 viruses and viral subtypes that are responsible for more than 85% of respiratory viral infections.
Pathologists at William Beaumont Hospital in Royal Oak, Michigan, are preparing for a dramatic change in how they test for respiratory viruses. By this time next month, the laboratory at the 1,061-bed major academic and referral center, will begin using the xTAG Respiratory Viral Panel (RVP) from Luminex Molecular Diagnostics to test for 12 respiratory viruses and viral subtypes.
This test is the first to use molecular technology to target respiratory viruses. Luminex announced 510(k) clearance for this assay on January 3, 2008. The test will be available for use by physicians practicing in the hospital. Beaumont Hospital’s laboratory outreach program will also offer the assay to office-based physicians.
Specimens are collected from a patient by the use of a nasopharyngeal swab. After multiplex PCR amplification of the specimen’s nucleic acid with target-specific primers, the xTAG RVP test can detect a respiratory virus (if present) within eight hours. This method is a significant improvement over current viral testing methods, which can take four to seven days.
“This test represents a fascinating transition in laboratory medicine where we go from doing cultures of viruses to actually detecting the viral genetic makeup,” said Mark D. Kolins, M.D., Chair of Clinical Pathology at Beaumont Hospital, Royal Oak, and Medical Director of the Beau- mont Reference Laboratory. “This is an example of how new assays based on molecular techniques can offer clinicians faster and more precise results.
Results In Eight Hours
“The big advantage is in terms of time,” Kolins explained. “Culturing a viral sample can take four to seven days. The xTAG RVP can produce a result in eight hours, which could be the same day for a patient in the hospital.
“The concern about viral infections is not so much when a patient is at the beginning of a cold or respiratory infection, because we have all been taught to wait a few days before seeing the doctor,” continued Kolins. “This technology is useful when a patient has progressively worse symptoms over a number of days and is at a point where we are considering treatment. That patient may need to be hospitalized with respiratory insufficiency. At that point, this test can help guide the physician because we can distinguish certain viruses, and we can decide if the virus is susceptible to certain antiviral therapy.
Bacterial or Viral?
“If a bacterial infection is detected through bacterial culture, that patient needs to be treated with antibiotics,” Kolins said. “If no bacteria are present, it is inappropriate to use antibiotics for a viral illness. Such inappropriate use leads to bacterial resistance, which is a major problem in healthcare. This multiplex test can put a dent in our use of inappropriate antibiotics by identifying the patient’s condition accurately and guiding selection of the right therapy.
“During the past year, we were one of four laboratories that helped Luminex validate the test,” he explained. “Now, we are acquiring additional equipment to go live with this test in the clinical setting.
“From the patients’ perspective, this is a non-invasive test and they can be seen in any office, an emergency clinic, outpatient clinic, or in the hospital,” Kolins added. “We will also use it in our Emergency Center for those patients who come in with more severe respiratory disorders. We are planning to introduce this test to our laboratory outreach program, which performs 4.5 million tests per year and is one of the largest in the nation. We think it will give us a competitive advantage in our outreach market.”
THE DARK REPORT observes that this new multi-analyte assay demonstrates the speed with which molecular technology can suddenly give laboratories new tools that increase diagnostic accuracy and produce a faster answer.
Multiplex Test Can Detect 12 Different Viruses & Subtypes
COLOR-CODED MICRO BEAD TECHNOLOGY LIES at the heart of the new multi-analyte xTAG Respiratory Viral Panel (RVP), recently cleared by the FDA and offered by Luminex Molecular Diagnostics of Toronto, Canada.
A sample containing viruses from a patient’s nasal cavity, throat, sinuses, or bronchi is collected. Nucleic acid is extracted from viruses in the sample and amplified using PCR (polymerase chain reaction).
The amplified DNA is mixed with short sequences (TAG primers) of DNA specific to each viral target. If the target is present, the primer will bind and be labeled. Color-coded beads are added to identify the tagged primers. Attached to each bead is an anti-TAG sequence specific to one of the extended TAG primers.
Samples are placed in a Luminex xMAP instrument where lasers identify the color, then read the reaction of the bead (specific to a virus or subtype). xTAG RVP tests for:
- Influenzas A, A-H1, A-H3, and B
- Adenovirus, responsible for about 10% of respiratory infections and multiple deaths
- Respiratory syncytial virus (RSV) A and B, the most common cause of bronchiolitis and pneumonia in infants and children
- Metapneumovirus, a virus that causes flu-like symptoms and a leading cause of respiratory infection in children
- Parainfluenza 1, 2, and 3, source of upper or lower respiratory infections in adults and children, such as croup, bronchiolitis, and bronchitis
- Rhinovirus, a cause of the common cold.