What is the role of direct immunofluorescent and serologic testing in the diagnosis of influenza?

Updated: Aug 07, 2020
  • Author: Hien H Nguyen, MD, MS; Chief Editor: Michael Stuart Bronze, MD  more...
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Some laboratories offer direct immunofluorescent tests on fresh specimens, but these tests are labor- and personnel-intensive and are less sensitive than culture methods. In order to overcome the expensive and time-consuming obstacle of culturing, several serologic tests have become available. In reality, many of these are not bedside tests; generally, 30-60 minutes are required to perform the test’s multiple steps. Test sensitivities generally range from 60-70%.

A study by Haran et al suggests that cytokine markers may help distinguish influenza from bacterial pneumonia or other viral respiratory infections. In this study, differences were observed between the bacterial pneumonia group, on one hand, and all other viral infections grouped together, on the other, with regard to interleukin (IL)-4, IL-5, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon gamma levels. However, IL-10 concentrations were uniquely elevated in patients with influenza (88.69 pg/mL) as compared with all other groups combined (39.19 pg/mL; P = .003). [40]

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