12/27/2017: Lab Advisory: Seasonal Influenza A(H3N2) Activity and Antiviral Treatment of Patients with Influenza

Audience: Clinical and public health laboratory partners.

Subject: CDC Health Advisory on Seasonal Influenza A(H3N2) Activity and Antiviral Treatment of Patients with Influenza.

Region: U.S. laboratory professionals.

Highlights for laboratory professionals: There are a few sections for laboratory professionals to note regarding testing.

• CDC is encouraging clinicians to start their patients on antiviral treatments as soon as possible after illness onset; this should not be delayed even for a few hours to wait for the results of testing.
• Information to assist clinicians about influenza testing decisions is available at https://www.cdc.gov/flu/professionals/diagnosis/consider-influenza-testing.htm. The most accurate influenza tests are molecular assays. Rapid molecular assays are available in clinical settings that can detect influenza virus nucleic acids in respiratory specimens in 15-30 minutes with high sensitivity and specificity. Other approved molecular assays can yield results in 60-80 minutes or in several hours with very high sensitivity and specificity.
• For hospitalized patients with suspected influenza, molecular assays are recommended. Information on influenza molecular assays is available at https://www.cdc.gov/flu/professionals/diagnosis/molecular-assays.htm. Rapid influenza diagnostic tests (RIDTs) with an analyzer device can detect influenza A and B viral nucleoprotein antigens in respiratory specimens in 10-15 minutes with moderate sensitivity, and RIDTs without an analyzer device have low to moderate sensitivity compared with reverse transcription-polymerase chain reaction (RT-PCR).
• Proper interpretation of influenza testing results is important to guide optimal management of influenza patients. An algorithm to assist clinicians in interpreting the results of influenza testing when influenza viruses ARE circulating in the community is available at https://www.cdc.gov/flu/professionals/diagnosis/algorithm-results-circulating.htm. Clinicians should be aware that a negative RIDT result does not exclude a diagnosis of influenza in a patient with suspected influenza when there is influenza activity in the community. Other factors such as the quality of the specimen, the source of the specimen in the respiratory tract, and the timing of specimen collection in relationship to illness onset, may also affect test results.

To learn more: Visit the HAN webpage.