Which specimen should be collected for respiratory syncytial virus (RSV) testing?

RSV Specimen Collection

For RSV testing, collect a nasopharyngeal swab as the primary specimen in most patients, but obtain lower respiratory tract specimens (bronchoalveolar lavage or endotracheal aspirate) in immunocompromised adults and critically ill patients where upper tract sampling is insufficient. 1

Standard Specimen Collection for Immunocompetent Patients

Nasopharyngeal swabs are the most commonly FDA-approved specimen type for RSV nucleic acid amplification testing (NAAT). 1

Acceptable Upper Respiratory Specimens (in order of preference):

• Nasopharyngeal swab (preferably flocked swabs for optimal viral recovery) 1
• Nasal swabs 1
• Nasal aspirates or nasal washes 1
• Pooled bilateral nasopharyngeal with throat swabs (often preferred over nasopharyngeal aspirates for upper respiratory tract infections) 1

Research evidence demonstrates that nasal swabs, throat swabs, and nasopharyngeal swabs show almost perfect agreement (κ > 0.8) with detection rates between 93-95% for RSV, making the less invasive nasal or throat swabs adequate alternatives to nasopharyngeal swabs. 2

Critical Exception: Immunocompromised and Critically Ill Patients

In immunocompromised adults—particularly hematopoietic stem cell transplant recipients—and critically ill patients, lower respiratory tract specimens are markedly more sensitive than upper respiratory samples and must be obtained when RSV infection is suspected. 1

Sensitivity Comparison in Immunocompromised Adults:

• Bronchoalveolar lavage (BAL): 88.9% 1
• Endotracheal aspirate: 71.4% 1
• Nasal wash: 15% 1

This dramatic difference in sensitivity means that upper respiratory tract testing alone will miss the majority of RSV infections in immunocompromised patients. 1 Although RSV shows relatively high concordance (92%) between upper and lower respiratory specimens compared to other respiratory viruses, lower tract sampling remains superior for accurate diagnosis in high-risk populations. 1

When to Obtain Lower Respiratory Specimens:

• Immunocompromised patients (transplant recipients, patients with hematologic malignancies) 1
• Critically ill patients with suspected lower respiratory tract infection 1
• Patients with severe underlying cardiopulmonary disease and lower tract symptoms 1

Specimen Handling and Transport

Place specimens in sterile containers or viral transport medium and transport at room temperature within 2 hours of collection. 3

For viral culture (when performed), specimens should preferably be transported on wet ice within 2 hours to maintain viral viability. 3

Testing Methodology Considerations

Most FDA-cleared multiplex respiratory panels are approved specifically for nasopharyngeal swabs, with some exceptions like the FilmArray Pneumonia Panel that is approved for BAL fluid. 1

If your laboratory chooses to use specimen types other than those FDA-cleared for a particular assay, verification studies documenting acceptable performance are required. 1 This is particularly important because failure to adhere to FDA label requirements can lead to inaccurate results and reimbursement denials. 1

Common Pitfalls to Avoid

Do not rely solely on upper respiratory specimens in critically ill or immunocompromised patients—the sensitivity is unacceptably low and will result in missed diagnoses with potentially fatal consequences. 1

Do not assume that a negative upper respiratory tract test excludes RSV in high-risk patients—progression of RSV from upper to lower respiratory tract in immunocompromised adults portends higher morbidity and mortality, and lower tract testing is essential. 1

Avoid using tracheal aspirates when BAL is feasible—BAL is preferred over tracheal aspirates for diagnosis of lower respiratory tract infection. 1