OBJECTIVES: Influenza virus and Respiratory Syncytial Virus (RSV) cause acute respiratory tract infections that present with similar symptoms. Although no PRO measures have been developed to monitor the severity of RSV symptoms in adults, influenza symptom PRO measures may be useful for RSV severity assessment. This study was conducted to evaluate the content validity of RSV adaptations of the FLU-PRO™ and Flu-iiQ™ (RI-PRO™ and R-iiQ™, respectively) for research in inpatients and outpatients with RSV infection.

METHODS: Combined concept elicitation and cognitive debriefing interviews were conducted with 28 US-English-speaking adults recently diagnosed with RSV (n=18) or influenza (n=10). Atlas.Ti was used for thematic analysis of verbatim transcripts.

RESULTS: Similar symptoms were reported for RSV and influenza: ‘cough’, ‘wheezing’ and ‘fever’ were discussed by >75% of RSV and influenza patients. Some RSV patients (17%) also noted ‘rapid heartbeat’, ‘dry nose’, and ‘dry eyes.’ RSV patients understood both measures and confirmed both PROs assessed most ‘core’ RSV symptoms. The RI-PRO™ assessed more symptoms patients reported including ‘body/systemic’, ‘nasal’, ‘eye’ and ‘pain’ than the R-iiQ™, but not ‘wheezing.’ The R-iiQ™ symptom assessment was less comprehensive and some impact items were not relevant for inpatients. When symptoms were most severe, most RSV patients stated it would have been difficult for them to complete either measure.

CONCLUSIONS: Robustly measuring RSV severity in adults is challenging. Content validity of RI-PRO™ and R-iiQ™ was supported, but neither measure provided the ideal assessment of symptoms for use in both inpatient/outpatient settings. Regulatory and best-practice guidelines highlight the need for a comprehensive symptom assessment to support content validity must be balanced with patient burden (e.g., brief symptom diaries) to monitor symptom severity daily or more often for severely ill hospitalized patients. This study identified symptoms most important to patients to include in a symptom diary for RSV inpatients and outpatients.