OBJECTIVES: A new self-report tool, the RSV Infection Intensity Impact Questionnaire (RSV-iiiQ), was adapted from an existing influenza symptom instrument (Osborne et al, 2011) consistent with FDA patient-focused drug development draft guidance. The RSV-iiiQ includes 29 questions in four hypothesized subscales (Respiratory Symptoms/Systemic Symptoms/Daily Activity Impacts/Emotional Impacts). The study aim was to evaluate preliminary psychometric properties of the RSV-iiiQ.
METHODS: A web-based, repeated cross-sectional observational study was conducted over two consecutive days in a convenience sample of US participants from 2 clinics and 2 qualitative research facilities, with laboratory-confirmed RSV at various severities. Participants were recruited within 21 days of an RSV medical encounter. Data from 111 adults (mean 44 years;78.4% female) were analyzed. Participants completed the RSV-iiiQ, Patient Global Impression of Severity (PGIS) and Change (PGIC) questions, the Sheehan Disability Scale (SDS), and the EQ-5D-5L. Measurement structure, internal consistency, test-retest reliability, construct/discriminating validity, and responsiveness of the RSV-iiiQ scale scores were evaluated.
RESULTS: Four single-factor confirmatory factor analysis models showed high loadings (0.63-0.96) and acceptable fit (CFI>0.95, SRMR<0.60, RMSEA=0.102-0.142). Test-retest reliability (stable subset based on PGIC ratings) was satisfactory (ICC≥0.65), as was internal consistency (alphas≥ 0.86) for all scales. Moderate to strong correlations were observed between RSV-iiiQ scale scores and corresponding SDS and the EQ-5D-5L scores (|r|=0.34-0.76). The RSV-iiiQ discriminated well between participants with varying symptom severity, number of days since RSV diagnosis, and SDS scores. Despite short study duration, moderate (r=0.31-0.38) correlations were observed between all RSV-iiiQ subscale change scores (except for Systemic Symptoms) and PGIS change.
CONCLUSIONS: Initial findings show the RSV-iiiQ is reliable, related to other variables in expected ways, and importantly, the original psychometric structure was reproduced. Further studies are needed in the context of a future vaccine or treatment trial to determine the RSV-iiiQ’s responsiveness to change over longer follow-up periods and develop thresholds for meaningful score changes.
