What is the approach to a nasal examination for a patient presenting with symptoms of influenza, considering potential complications and underlying conditions such as asthma or Chronic Obstructive Pulmonary Disease (COPD)?

Nasal Examination Approach for Influenza

For patients presenting with influenza symptoms, collect a nasopharyngeal specimen using a flocked swab as the first-line approach, obtained as soon after illness onset as possible and preferably within 4 days of symptom onset. 1

Specimen Collection Priority (in order of preference)

Nasopharyngeal specimens are the gold standard and should be collected over all other upper respiratory tract specimens to maximize detection of influenza viruses. 1

If nasopharyngeal specimens cannot be obtained:

• Collect both nasal and throat swab specimens and combine them together for testing, rather than using single specimens from either site alone 1
• Mid-turbinate nasal swab specimens should be collected over throat swabs alone if only one site can be sampled 1

Use flocked swabs over non-flocked swabs to improve detection of influenza viruses. 1

Special Considerations for High-Risk Patients

Patients with Asthma or COPD

Test immediately for influenza in patients presenting with acute worsening of chronic cardiopulmonary disease (COPD, asthma) during influenza activity, as influenza can trigger exacerbations of underlying conditions even without classic influenza symptoms. 1

• These patients may present with acute onset of respiratory symptoms with or without fever 1
• Exacerbations may manifest as non-pneumonic bacterial exacerbation of chronic lung disease, possibly with mixed viral infection 1
• Testing should influence clinical management decisions regarding antiviral therapy 1

Immunocompromised Patients

Collect specimens from both upper and lower respiratory tracts in immunocompromised patients, as they may shed virus for weeks to months and present with atypical manifestations. 1, 2

• The infectious period can extend well beyond the typical 5-day window 1, 2
• Specimen collection beyond 5 days after illness onset may still yield positive results 1
• Consider bronchoalveolar lavage specimens in addition to nasopharyngeal specimens 1

Timing of Specimen Collection

Collect specimens as soon after illness onset as possible, preferably within 4 days of symptom onset for outpatients. 1

• In immunocompetent adults and older children, viral shedding decreases substantially after 5 days, potentially leading to false-negative results 1
• Infants and young children may shed virus for ≥1 week, allowing for a longer collection window 1
• For hospitalized patients, collect specimens as soon as possible regardless of symptom duration 1

Specimen Handling

Refrigerate specimens immediately (without freezing) until analysis and process as soon as possible after collection. 1

Transport specimens rapidly to the laboratory to maintain viral viability and optimize detection. 1

Testing Methodology

Use rapid molecular assays (RT-PCR or other nucleic acid amplification tests) over rapid influenza diagnostic tests (RIDTs) in hospitalized patients to improve detection. 1, 3

• RIDTs may be used in outpatients to improve detection over clinical diagnosis alone 1
• For hospitalized patients, if RIDTs are the only available option, follow up negative results with RT-PCR or other molecular assays 1
• Consider multiplex RT-PCR assays targeting a panel of respiratory pathogens in immunocompromised hospitalized patients 1, 3

Specimens NOT to Collect

Do not collect or routinely test specimens from nonrespiratory sites such as blood, plasma, serum, cerebrospinal fluid, urine, or stool for influenza diagnosis. 1

Do not collect serum specimens for serological diagnosis of seasonal influenza for clinical management purposes, as results cannot be obtained in time to influence treatment decisions. 1

Common Pitfalls to Avoid

Do not rely solely on throat swabs, as they have significantly lower sensitivity than nasopharyngeal or mid-turbinate nasal specimens. 1

Do not delay specimen collection in high-risk patients (immunocompromised, chronic cardiopulmonary disease, age <2 years or ≥65 years) even if presenting beyond the typical 4-day window, as testing may still influence management. 1, 2

Do not assume absence of fever rules out influenza in immunocompromised patients or those with chronic conditions, as they may present with atypical manifestations. 1, 2

Do not wait for laboratory confirmation before initiating antiviral therapy in hospitalized patients, severely ill patients, or high-risk groups presenting during influenza season. 3, 4