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Recent reports from Australia of Tamiflu resistance among 2009 H1N1 flu viruses, from Asia of the emergence of a mutant strain of H5N1 bird flu, and from the United States about two children infected with a new variant of a swine flu underscore a fundamental truth about influenza: the only thing that is predictable about influenza is its unpredictability. We know that every year one or more seasonal flu viruses will circulate through the community and cause disease, but we can never be confident in our ability to predict its timing or severity, nor can we know when and where the next pandemic strain will emerge.
As we prepare for the 2011-2012 flu season, laboratory professionals must recognize that influenza causes significant disease and death in our patients every year and that we cannot discount the important role we play in providing quality influenza testing to clinicians. These services can mitigate the potential for a health crisis by aiding in the identification and management of infected patients and also reducing the spread of disease to others.
It is also important that laboratorians recognize that when it comes to influenza testing, not all tests are equal. The rapid immunoassay-based tests commonly used in some Emergency Departments and Urgent Care Centers provide results quickly, and are used to segregate infected patients from uninfected ones and make decisions regarding the use of specific anti-viral therapy to high-risk patients, such as pregnant women, young children, and patients with compromised immune systems. However, the sensitivity of rapid tests ranges from 30% to 70%, meaning that too many infected patients have false negative results. It is vital for clinicians to understand that a negative rapid test does not exclude the diagnosis of influenza. That's important because studies have shown that a delay in the initiation of anti-viral therapy in high-risk patients is associated with an increased likelihood of the need for critical care and of death.
Molecular testing by polymerase chain reaction (PCR) has now been established as a sensitive method of influenza testing. The American Society for Microbiology has indicated that PCR-based methods and viral cell culture are preferred methods for influenza testing. Until recently, molecular testing has been largely limited to reference laboratories, which unfortunately required clinicians to wait for results. The 2009 H1N1 pandemic highlighted the limitations of rapid tests and accelerated innovation in high-end molecular testing. Now, hospital and other labs can run PCR-based test kits (such as the Simplexa assays on the 3M Integrated Cycler) “nearer the patient” for accurate and timely results.
The future of influenza testing and, indeed, of respiratory virus testing in general, is molecular. Continuing innovations that make molecular testing easier to perform will make such testing accessible in more settings than just the reference laboratory or the hospital lab. The availability of sensitive molecular assays nearer to the patient will provide clinicians with reliable information more quickly to help guide management of their patients. Prompt, reliable diagnoses will benefit patients because they will be more likely to be prescribed appropriate anti-viral therapy and less likely to receive unnecessary therapies such as antibiotics.
While the unpredictability of influenza will always pose challenges for patients, clinicians, and laboratorians, access to better tests and more widespread use of influenza vaccines offer the best hope to reduce the impact of the flu for this upcoming season and beyond.
Jay M. Lieberman, MD, is Medical Director, Infectious Disease, for Quest Diagnostics.
MLO's “Management Q&A” column provides practical solutions to readers' laboratory management issues from experts in various fields. Readers may send questions to [email protected].
