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Table 3 Influenza diagnostic tests

From: Influenza virus-related critical illness: prevention, diagnosis, treatment

Influenza testing modality[49, 56]MethodTime to resultsSensitivitySpecificityRespiratory specimens*
SwabWash/fluidAspirate
Molecular assay (Rapid)**#Nucleic acid amplification10–15 minModerate to highHighNP or nasalN/AN/A
Molecular assay**#Nucleic acid amplification15–30 minHighHighNP or throatNP or BAL/mini BALNasal or endotracheal
Rapid influenza diagnostic Test (RIDT)Antigen detection10–15 minLow to moderateHighNP, nasal, throatNP or nasalNP or nasal
Immunofluorescence assay (direct and indirect)Antigen detection1–4 hModerateHighNPNPNasal
Rapid cell culture (shell vials; cell mixtures)Virus isolation1–3 daysHighHighNP or throatNP or BAL/mini BALNasal or endotracheal
Tissue cell viral culture (conventional)Virus isolation3–10 daysHighHighNP or throatNP or BAL/mini BALNasal or endotracheal
  1. *FDA-approved clinical specimens vary by specific test; refer to the manufacturer’s package insert for each test’s approved specimens
  2. **Recommended for testing hospitalized patients with suspected influenza. Some molecular assays also detect other respiratory pathogens
  3. #Patients with respiratory failure and suspected influenza should have lower respiratory tract specimens collected and tested, including if upper respiratory tract specimens are negative for influenza because a patient may have cleared influenza virus from the upper respiratory tract and continue to have influenza viral replication in the lower respiratory tract
  4. NP nasopharyngeal, BAL bronchoalveolar lavage
  5. Serologic testing is not recommended for diagnosis or clinical management of patients with suspected influenza