Reliability of RSV Antigen Diagnostic Tests in the Presence of Nirsevimab.

Background: Nirsevimab is approved for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants. Although nucleic acid detection by polymerase chain reaction is primarily utilized for the clinical diagnosis of RSV, antigen detection is still routinely used and primarily relies on direct interaction with the RSV F protein in patient nasal samples. While expected monoclonal antibody (mAb) levels in nasal samples are typically <1 μg/mL following administration, some mAbs targeting the RSV F protein, such as palivizumab, have been shown to interfere with antigen detection. We assessed whether the presence of nirsevimab in nasal samples may interfere with RSV detection by antigen tests.

Methods: RSV detection was evaluated in 6 antigen detection tests utilizing contrived samples containing RSV A or B, and nirsevimab at 2 concentrations (1 or 10 µg/mL) chosen to estimate and exceed physiologically relevant concentrations. To better simulate real-world diagnostic specimens, RSV-positive nasal samples were pooled and assessed in the presence of nirsevimab in 2 frequently utilized detection tests.

Results: RSV was detected in contrived samples by all diagnostic kits evaluated in the presence of nirsevimab at both concentrations. Furthermore, RSV was detected in all nasal specimen pools by both diagnostic tests and remained detectable in the presence of nirsevimab at both concentrations tested, displaying 100% agreement with nonspiked pools.

Conclusions: Nirsevimab did not interfere with RSV detection with any of the antigen tests evaluated, suggesting patients who receive nirsevimab are unlikely to require alternative assays for clinical RSV diagnosis.