Is it a cold? Or is it the flu?
That’s the question primary care providers face as the 2017-2018 flu season gets underway. Many will use diagnostic tests to make the determination and prescribe an appropriate course of action.
The flu and the common cold are both respiratory illnesses, but they are caused by different viruses, according to the Centers for Disease Control and Prevention. Because they have similar symptoms, it can be difficult to tell the two apart. And even though most people who develop influenza recover in several days to less than two weeks, some develop serious complications. Hence the need for rapid diagnosis.
Young children, adults aged 65 years and older, pregnant women, and people with certain chronic medical conditions are among those at highest risk of serious flu complications, including inflammation of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues, and multi-organ failure (for example, respiratory and kidney failure). Flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s life-threatening response to infection.
Flu also can make chronic medical problems worse. For example, people with asthma may experience attacks when they have flu, and people with chronic heart disease may experience a worsening of this condition triggered by flu.
Tools for detection
Repertoire readers have a variety of flu detection tools to offer their physician customers.
Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory specimens, and display the result in a qualitative way (positive vs. negative), according to CDC. The reference standards for laboratory confirmation of influenza virus infection in respiratory specimens are reverse transcription-polymerase chain reaction (RT-PCR) or viral culture. RIDTs can yield results in less than approximately 15 minutes. However, RIDTs have limited sensitivity to detect influenza viruses in respiratory specimens compared to RT-PCR or viral culture, and negative RIDT test results should be interpreted with caution given the potential for false negative results, especially during peak influenza activity in a community, says CDC.
Some practices use analyzer reader devices to standardize result interpretation of their rapid tests. Such devices can reduce the possibility of human error in interpreting the results.
Molecular assays are increasingly being used in clinical settings, according to CDC. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and other molecular assays can identify the presence of influenza viral RNA in respiratory specimens. Some molecular assays are able to detect and discriminate between infections with influenza A and B viruses; other tests can identify specific seasonal influenza A virus subtypes [A(H1N1)pdm09, or A(H3N2)].
Repertoire asked manufacturers of flu diagnostics to share the high points of their offerings. Their responses follow:
Sidebar: Flu vaccine via microneedles
A National Institutes of Health-funded study led by a team at the Georgia Institute of Technology and Emory University has shown that an influenza vaccine can produce robust immune responses and be administered safely with an experimental patch of dissolving microneedles.
The vaccine patch consists of 100 solid, water-soluble needles that are just long enough to penetrate the skin. Adhesive helps the patch grip the skin during the administration of the vaccine, which is encapsulated in the needles and is released as the needle tips dissolve, within minutes. The patch is peeled away and discarded. (After vaccination, imaging of the used patches found that the microneedles had dissolved in the skin, suggesting that the used patches could be safely discarded as non-sharps waste.)
The results showed that antibody responses generated by the vaccine, as measured through analysis of blood samples, were similar in study groups vaccinated using patches and those receiving intramuscular injection, and these immune responses were still present after six months.
The vaccines remained potent in the patches without refrigeration for at least one year.
The study, published June 27, 2017, in The Lancet, was led by Nadine Rouphael, M.D., associate professor of medicine and Mark J. Mulligan, M.D., distinguished professor of medicine, Emory University School of Medicine, in collaboration with Mark R. Prausnitz, Ph.D., Regents Professor and J. Erskine Love Chair in Chemical and Biomolecular Engineering, Georgia Institute of Technology. Prausnitz is an inventor and has ownership interest in companies developing microneedle products, including Micron Biomedical.
The team plans to conduct further clinical trials to pursue the technology’s ultimate availability to patients. They also are working to develop microneedle patches for use with other vaccines, including measles, rubella and polio.