Influenza other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

Overview

Other diagnostic test for influenza include molecular assays, such as RT-PCR. New technologies being pursued include those that examine influenza viruses at the molecular level. By examining the genetic makeup of influenza viruses, such tests could identify both the virus type and subtype simultaneously.

Other Diagnostic Studies

Molecular Assays Adapted from CDC

• Tests for influenza include molecular assays, rapid influenza diagnostic tests, viral culture or serology.
• Molecular assays for influenza are increasingly being used in clinical settings.
• Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and other molecular assays can identify the presence of influenza viral RNA in respiratory specimens.
• RT-PCR is particularly useful to identify influenza virus infection as a cause of respiratory outbreaks in institutions, such as nursing homes, chronic care facilities, and hospitals.
• Some molecular assays are able to detect and discriminate between infections with influenza A and B viruses; other tests can identify specific influenza A virus subtypes.
• These assays can yield results in 3-8 hours.
• Notably, the detection of influenza viral RNA by these assays does not always indicate detection of viable virus or on-going influenza viral replication.
• It is important to note that not all assays have been cleared by the FDA for diagnostic use.

Advantages	Disadvantages
Molecular assays are more sensitive and specific for detecting influenza viruses than other influenza tests (e.g., rapid influenza diagnostic tests, immunofluorescence, and viral culture) The likelihood of a false positive or false negative result is low and therefore, the interpretation of the result is less impacted by the level of influenza activity in the community Some, but not all molecular assays can distinguish between specific influenza A virus subtypes	Results of RT-PCR and other molecular assays may not be available in a clinically relevant time frame to inform clinical management decisions. RT-PCR and other molecular assays are generally not available for outpatient or emergency room settings. Respiratory specimens may need to be sent to a state public health laboratory or commercial laboratory for RT-PCR. Therefore, although the test can yield results in 3-8 hours, the actual time to receive results may be substantially longer. Most molecular assays are not approved to test lower respiratory tract specimens. RT-PCR and other molecular assays are generally more expensive. They may not specifically identify all of the subtypes of influenza A virus. Depending on the test, a negative result for one influenza A virus subtype may not preclude infection with another influenza A virus subtype. Some tests are not FDA-cleared and an evaluation has not been performed to assess the accuracy of all available RT-PCR and molecular assays.