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

Table 3 Influenza diagnostic tests

Influenza testing modality[49, 56]	Method	Time to results	Sensitivity	Specificity	Respiratory specimens*
Influenza testing modality[49, 56]	Method	Time to results	Sensitivity	Specificity	Swab	Wash/fluid	Aspirate
Molecular assay (Rapid)**#	Nucleic acid amplification	10–15 min	Moderate to high	High	NP or nasal	N/A	N/A
Molecular assay**#	Nucleic acid amplification	15–30 min	High	High	NP or throat	NP or BAL/mini BAL	Nasal or endotracheal
Rapid influenza diagnostic Test (RIDT)	Antigen detection	10–15 min	Low to moderate	High	NP, nasal, throat	NP or nasal	NP or nasal
Immunofluorescence assay (direct and indirect)	Antigen detection	1–4 h	Moderate	High	NP	NP	Nasal
Rapid cell culture (shell vials; cell mixtures)	Virus isolation	1–3 days	High	High	NP or throat	NP or BAL/mini BAL	Nasal or endotracheal
Tissue cell viral culture (conventional)	Virus isolation	3–10 days	High	High	NP or throat	NP or BAL/mini BAL	Nasal or endotracheal

*FDA-approved clinical specimens vary by specific test; refer to the manufacturer’s package insert for each test’s approved specimens
**Recommended for testing hospitalized patients with suspected influenza. Some molecular assays also detect other respiratory pathogens
#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
NP nasopharyngeal, BAL bronchoalveolar lavage
Serologic testing is not recommended for diagnosis or clinical management of patients with suspected influenza

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