Tests
Your Organizational Guidance
ebpracticenet urges you to prioritize the following organizational guidance:
Prévention de l’InfluenzaPublished by: Groupe de travail Développement de recommandations de première ligneLast published: 2018Preventie van influenzaPublished by: Werkgroep Ontwikkeling Richtlijnen Eerste Lijn (Worel)Last published: 20181st tests to order
clinical diagnosis
Test
There are no pathognomonic features of influenza, and further testing is indicated only when the results are likely to affect diagnosis and treatment decisions and to provide community disease surveillance.[84]
Result
febrile respiratory illness during a known seasonal influenza outbreak
Tests to consider
molecular assays
Test
Includes rapid molecular assays, reverse-transcription polymerase chain reaction (RT-PCR), and other nucleic acid amplification tests (NAATs).[84]
The Infectious Diseases Society of America recommends using rapid molecular assays for detection of influenza viruses in respiratory specimens of outpatients and RT-PCR or other molecular assays for detection in respiratory specimens of hospitalised patients.[2]
NAATs are the preferred method for detection of influenza virus in clinical samples because of their superior diagnostic sensitivity compared to rapid antigen tests.[91]
Nasopharyngeal specimens are recommended for a respiratory specimen for viral isolation.[2]
Result
detection of influenza virus; some assays can identify influenza virus types and specific influenza A virus subtypes
antigen detection tests
viral culture
Test
Definitive test for laboratory diagnosis, but takes 3-10 days for results to be reported, so is not often used for initial clinical management. It is used for confirming screening tests and for public health surveillance.
Shell vial (centrifuge-enhanced) culture, if available, may reduce time for results to 1-3 days.[84]
Acceptable specimens include throat or nasopharyngeal swab, nasopharyngeal aspirate or wash, and sputum.[91]
Result
detection of influenza virus or viral antigen
serology
Test
Detects influenza A and B.
Assesses paired acute (collected within the first week of illness) and convalescent (collected 2-4 weeks after the acute sample) serum samples.
Positive test result is indicative of recent infection.
May take 2 or more weeks to receive results.
It is not recommended for accurate clinical decision-making.[84]
Result
fourfold or greater rise in antibody titre from acute to convalescent sample
chest x-ray
Test
Should be done if either a primary viral or secondary bacterial pneumonia is suspected.
The radiographic appearances of community-acquired pneumonia include lobar consolidation, interstitial infiltrates, and cavitations.
It is commonly thought that lobar consolidation is suggestive of bacterial pneumonia and interstitial infiltrates are suggestive of pneumonia due to Pneumocystis jirovecii (formerly P carinii) and viruses. However, radiologists cannot reliably differentiate bacterial from non-bacterial pneumonia on the basis of the radiographic appearance alone.[100]
Result
normal in uncomplicated cases; may show infiltrates consistent with pneumonia in complicated cases
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