Diagnosis of RSV Infection in Adults

Diagnostic Testing Methods

• The American Thoracic Society and the Infectious Diseases Society of America recommend using nucleic acid amplification testing (NAAT/RT-PCR) from nasopharyngeal swabs or nasal aspirates for diagnosing RSV infection in adults, as it is the most sensitive diagnostic method 1, 2
• The Infectious Diseases Society of America suggests obtaining specimens from nasopharyngeal swabs, nasal aspirates, nasal washes, or throat swabs for RSV diagnosis in adults 2, 3
• For immunocompromised adults with suspected lower respiratory tract infection, the American College of Chest Physicians recommends testing lower respiratory specimens (BAL fluid, endotracheal aspirate) as they are significantly more sensitive than upper respiratory samples (BAL: 88.9% vs. nasal wash: 15%) 1

Available Testing Platforms

• The American College of Chest Physicians recommends using multiplex PCR panels that detect influenza, RSV, and other respiratory viruses plus atypical bacteria (e.g., FilmArray Pneumonia Panel, ePlex Respiratory Pathogen Panel) for diagnosing RSV infection in adults 1
• The Infectious Diseases Society of America suggests using multiplex PCR for respiratory viruses only (>4 targets) or targeted multiplex PCR for influenza A/B plus RSV (e.g., Xpert Flu/RSV XC) for diagnosing RSV infection in adults 1

Alternative Diagnostic Methods (Less Sensitive)

• The American Geriatrics Society notes that rapid antigen detection tests have poor sensitivity in adults (40-80% for influenza, likely similar for RSV) due to lower viral loads compared to children 4, 5
• The Infectious Diseases Society of America recommends against using serology for acute diagnosis of RSV infection in adults, as high seroprevalence indicates past exposure, and it is only useful for epidemiological studies 2

When to Test for RSV

• The American College of Physicians recommends testing adults presenting with new onset respiratory symptoms, such as cough, nasal congestion/discharge, shortness of breath, or sore throat, especially during RSV season (typically December-March in Northern Hemisphere) 3
• The Infectious Diseases Society of America suggests testing high-risk groups, including patients with chronic cardiac or pulmonary disease, immunocompromised individuals, and residents of long-term care facilities 2, 5

Clinical Presentation Considerations

• The American Thoracic Society notes that RSV infection in adults typically presents with nasal congestion, cough, wheezing, and low-grade fever, but clinical features overlap significantly with other respiratory viruses, making laboratory confirmation essential 5

Critical Diagnostic Pitfalls to Avoid

• The Infectious Diseases Society of America recommends against relying on clinical features alone to distinguish RSV from influenza or other viral infections, and emphasizes the importance of laboratory confirmation 5
• The American College of Chest Physicians suggests not using single upper respiratory tract specimens in critically ill or immunocompromised patients, and recommends testing lower respiratory specimens for higher sensitivity 1
• The American Geriatrics Society notes that negative rapid antigen tests should not be accepted as definitive, and recommends confirming with NAAT if clinical suspicion remains high 4, 5

Diagnostic Strategies for Respiratory Syncytial Virus (RSV) Infection

Primary Diagnostic Modality

• Nucleic acid amplification testing (NAAT/RT‑PCR) performed on a nasopharyngeal swab is the most sensitive method available and should be used as the first‑line diagnostic test for RSV in all patient groups. 6
• FDA‑cleared NAAT platforms, including multiplex panels such as the FilmArray Respiratory Panel, ePlex Respiratory Pathogen Panel, and Xpert Flu/RSV XC, can simultaneously detect RSV together with other respiratory viruses. [6][7]

Specimen Collection Recommendations

Immunocompetent patients with upper‑respiratory symptoms

• A nasopharyngeal swab or nasal aspirate alone provides adequate material for NAAT/RT‑PCR. 6
• Specimens should be placed in a sterile container or viral transport medium and kept at room temperature, with transport to the laboratory within 2 hours. 6

Immunocompromised patients or those with lower‑respiratory‑tract infection

• In addition to an upper‑respiratory sample, obtain a lower‑respiratory specimen (bronchoalveolar lavage fluid or endotracheal aspirate); lower‑tract samples are markedly more sensitive (BAL ≈ 89 % vs. nasal wash ≈ 15 %). 7
• Upper‑respiratory testing alone frequently misses RSV infections in immunocompromised adults. 7

Alternative Testing Methods (when NAAT unavailable)

• Rapid antigen detection tests have a sensitivity of 80–95 % in children but are less reliable in adults; they should not be used as the sole diagnostic tool. 8
• Direct fluorescent antibody (DFA) staining can provide results within hours and may be acceptable for rapid screening when NAAT is not accessible, although its sensitivity is lower than that of NAAT. 6
• Viral culture is time‑consuming (cytopathic effect may require up to 2 weeks) and has largely been supplanted by molecular methods. [6][9]

Populations Requiring Targeted Testing

• Individuals with chronic cardiac or pulmonary disease should be prioritized for RSV testing during the typical season (December–March). 8
• Immunocompromised persons, including transplant recipients, require testing regardless of symptom severity. 6

Testing Pitfalls and Infection‑Control Measures

• In critically ill or immunocompromised patients, upper‑respiratory specimens alone are insufficient; lower‑respiratory samples must be collected to achieve higher diagnostic yield. 7
• Multiplex PCR panels may exhibit reduced sensitivity for RSV compared with single‑target NAAT assays; clinicians should be aware of this limitation. [10][11]
• When RSV infection is suspected based on clinical presentation and epidemiology, implement contact isolation precautions while awaiting laboratory confirmation. 8

RSV Diagnostic Testing: Evidence‑Based Recommendations

Diagnostic Modality Selection

• Nucleic acid amplification testing (NAAT/RT‑PCR) performed on a nasopharyngeal swab or nasal aspirate is the gold‑standard, first‑line test for RSV across all patient populations. Evidence indicates superior sensitivity compared with culture and antigen methods. 12
• NAAT/RT‑PCR is the most sensitive diagnostic modality, exceeding the sensitivity of viral culture and antigen detection. High analytical sensitivity supports its use as the preferred assay. 12
• FDA‑cleared multiplex PCR platforms (e.g., FilmArray Respiratory Panel, ePlex Respiratory Pathogen Panel, Xpert Flu/RSV XC) can simultaneously detect RSV together with influenza and other respiratory viruses. These panels provide comprehensive viral profiling in a single run. 13
• Acceptable NAAT methodologies include real‑time RT‑PCR, multiplex microarray hybridization, nested multiplex RT‑PCR, isothermal nucleic‑acid amplification, and loop‑mediated isothermal amplification (LAMP). All have demonstrated comparable performance for RSV detection. 13

Specimen Collection for Immunocompetent Patients

• Nasopharyngeal swab or nasopharyngeal aspirate/washing are the optimal upper‑respiratory specimens for detecting RSV in patients with upper‑respiratory symptoms. These specimens yield the highest detection rates. 12
• When nasopharyngeal collection is not feasible, combined throat‑nasal swabs are an acceptable alternative. This approach maintains adequate sensitivity. 13
• Specimens should be placed in sterile containers or viral‑transport medium and transported at ambient temperature within 2 hours of collection. Prompt handling preserves nucleic‑acid integrity. 12

Specimen Collection for Immunocompromised Adults

• In immunocompromised adults—particularly hematopoietic stem‑cell transplant (HSCT) recipients—lower‑respiratory‑tract specimens (bronchoalveolar lavage fluid or endotracheal aspirate) are markedly more sensitive than upper‑respiratory samples and should be obtained when RSV infection is suspected. This recommendation is based on comparative sensitivity data. 13
• Sensitivity of lower‑respiratory testing in this population: bronchoalveolar lavage ≈ 89 %, endotracheal aspirate ≈ 71 %, versus nasal wash only ≈ 15 %. The large disparity underscores the need for lower‑tract sampling. 13
• Although RSV shows a relatively high concordance (≈ 92 %) between upper‑ and lower‑respiratory specimens compared with other viruses, lower‑tract sampling remains superior for accurate diagnosis. High discordance for other viruses further supports this approach. 13

Alternative Diagnostic Methods (When NAAT Is Unavailable)

• Rapid antigen detection tests (direct fluorescent antibody or immunoassay) deliver results within ~4 hours but have significantly lower sensitivity than NAAT. Their limited performance restricts use to settings where NAAT is inaccessible. 12
• Viral culture, once considered the gold standard, now requires 2–5 days for results and has been largely supplanted by NAAT. Culture remains less sensitive but offers higher clinical specificity for active infection. 12
• For culture, specimens must be placed in sterile containers or viral‑transport medium and transported at room temperature—or preferably on wet ice—within 2 hours. Proper transport conditions are essential to maintain viral viability. 12