Influenza prevalence fluctuates seasonally with the onset of “flu season” typically beginning its upswing in the month of December. It is important for providers to have an awareness of influenza prevalence (in addition to other respiratory viruses) to help guide when influenza testing should be pursued.
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Influenza
Influenza prevalence fluctuates seasonally, and case numbers are currently increasing throughout West Michigan. The onset of “flu season” varies year-to-year though typically begins its upswing in the month of December. It is important for providers to have an awareness of influenza prevalence (in addition to other respiratory viruses) to help guide when influenza testing should be pursued.
The use of point of care (POC) antigen testing reduces both the cost to the patient and turn-around-time as compared to lab-based molecular methods. POC antigen tests are typically available for COVID-19, influenza A/B, and as a COVID-19/influenza A/B combination test. During warmer months when influenza prevalence is negligible yet COVID-19 may be circulating, a COVID-only antigen test may be helpful for diagnosis. As influenza increases into colder months, a COVID-19/Influenza A/B combo test would act as a screen for both viruses.
POC tests generally have high analytical specificity but lack the sensitivity of nucleic acid amplification methods (e.g. PCR). For this reason, PCR testing is still recommended for hospitalized patients and for outpatients with a negative POC result if influenza is still suspected and if the result will impact clinical decision making. Influenza PCR may be ordered as a standalone test (LAB3255) or as a part of a panel alongside COVID-19 and RSV (LAB1230746).
Test Information
- Influenza PCR Epic Code: LAB3255, Interface EMR Code: 11594, CPT Code 87502
- COVID-19, Influenza A/B, RSV PCR Epic Code: LAB1230746, Interface EMR Code: 1230746, CPT: 0241U
Contact/Resources
Local Infection Prevention Team
Michigan Department of Health and Human Services
- Resources: https://www.michigan.gov/flu/resources
- Surveillance information: https://www.michigan.gov/flu/surveillance
This winter, West Michigan influenza infections peaked in February 2024 and significantly declined throughout March and April 2024. Now with a low prevalence of circulating influenza, using the most sensitive diagnostic test is recommended in order to obtain accurate and actionable results. Influenza antigen testing (e.g. Sofia instrument) is no longer appropriate at this time and Influenza PCR testing should be ordered when clinically indicated.
| Low Influenza Prevalence |
High Influenza Prevalence |
|
| Recommended Order | Influenza PCR (LAB3255) | Influenza antigen testing (e.g. Sofia instrument) or Influenza PCR (LAB3255) |
More detailed information can be found as published by the CDC:
Influenza cases numbers are currently increasing throughout West Michigan. Influenza prevalence guides the most appropriate testing approach and sufficient prevalence has now been reached for influenza rapid antigen or point of care testing (e.g. Sofia instrument) to have improved performance. The use of point of care testing as a screening method during high prevalence reduces both the cost to the patient and turn-around-time as compared to lab-based molecular methods. Point of care tests generally have high analytical specificity, but lack the sensitivity of nucleic acid amplification methods (e.g. PCR). For this reason, PCR testing is still recommended for hospitalized patients and for outpatients with a negative result if influenza is still suspected and if the result will impact clinical decision making.
| Low influenza prevalence | High influenza prevalence | |
| Recommended order | Influenza PCR | Influenza Point of Care Testing or Influenza PCR |
This winter, West Michigan influenza infections peaked in December 2022 and significantly declined throughout February and March 2023. Now with a low prevalence of circulating influenza, using the most sensitive diagnostic test is recommended in order to obtain accurate and actionable results. Influenza antigen testing (e.g. Sofia instrument) is no longer appropriate at this time and Influenza PCR testing should be ordered when clinically indicated.
Compliance & Safety, Education & Training, General Information, Main lab, Test Utilization
Inform: RSV Testing – Age Restrictions
Respiratory syncytial virus (RSV) primarily infects pediatric patients, but occasionally infects adults and may be of particular concern for the elderly and immunocompromised. Corewell Health Laboratories offers two tests for RSV. A rapid antigen test may be used to confirm RSV diagnosis in pediatric patients. This test is not approved by the FDA for testing adult patients, so tests will be cancelled if ordered on an off-label age group. There are no age restrictions for RSV testing by way of a molecular panel that also includes COVID and influenza as viruses with overlapping symptoms.
| Test name | Epic Test ID | Methodology | Specimen | Age restriction |
| RSV Rapid | LAB495 | Antigen | Nasopharyngeal (NP) swab | Approved for patients 0 – 18 years of age |
| COVID, Influenza, RSV PCR | LAB1230746 | Molecular/PCR | Nasopharyngeal (NP) swab | No age restriction |
Influenza cases numbers are currently increasing throughout West Michigan. Influenza prevalence guides the most appropriate testing approach and sufficient prevalence has now been reached for influenza rapid antigen testing (e.g. Sofia instrument) to have improved performance. The use of rapid antigen testing as a screening method during high prevalence reduces both the cost to the patient and turn-around-time as compared to lab-based molecular methods. Rapid antigen tests generally have high analytical specificity, but lack the sensitivity of nucleic acid amplification methods (e.g. PCR). For this reason, PCR testing is still recommended for hospitalized patients and for outpatients with a negative antigen result if influenza is still suspected and if the result will impact clinical decision making.
Effective immediately, the following Regional Hospital Laboratories have the 4-Plex (COVID-19, Influenza A, Influenza B, RSV) test available for ordering and testing:
- Big Rapids Hospital Laboratory
- Blodgett Hospital Laboratory
- Gerber Hospital Laboratory
- Ludington Hospital Laboratory
- Pennock Hospital Laboratory
- Reed City Hospital Laboratory
- United/Greenville Hospital Laboratory
- Zeeland Hospital Laboratory
West Michigan influenza infections peaked mid-March 2022 and have been declining in the weeks that followed. Now with a low prevalence of circulating influenza, using the most sensitive diagnostic test is recommended in order to obtain accurate and actionable results. Influenza antigen testing (e.g. Sofia instrument) is no longer appropriate at this time and Influenza PCR testing should be ordered when clinically indicated.
| Low Influenza Prevalence |
High Influenza Prevalence |
|
| Recommended Order | Influenza PCR (LAB3255) | Influenza Rapid Antigen (LAB2111530) or Influenza PCR (LAB3255) |
More detailed information can be found as published by the CDC:
TEST INFORMATION
| Test name | Epic code | Interface EMR Code | CPT Code |
| Influenza PCR | LAB3255 | 11594 | 87502 |
| Influenza Rapid Antigen | LAB2111530 | 11208 | 87804 x4 |
Compliance & Safety, Education & Training, General Information
Appropriate Labeling for Shared Specimen – COVID-19 & FLU AB PCR
To provide efficient and safe testing for patient specimens, please review the following information when sending COVID-19 PCR and Influenza A/B PCR testing in the same encounter to Spectrum Health Laboratories.
Two labels will be available for this testing. Labels must be fixed so that
• The test and patient information are shown
• The barcode may be easily scanned by Lab staff or instruments
When this is not done correctly, Laboratory staff removes the labels and re-fixes or re-prints it, which obstructs workflow, causes delays, and could result in patient information being peeled off. With patient safety and efficient testing being two of the Lab’s top priorities, it is vital that specimens arrive in such a way as to best accomplish both.