Psychometric validity of the 22-item sinonasal outcome test in cystic fibrosis

BACKGROUND: The 22-item sinonasal outcome test (SNOT-22) is widely used to evaluate quality of life (QOL) in cystic fibrosis chronic rhinosinusitis (CF-CRS) but lacks formal validation in people with CF (PwCF). This study explores the psychometric properties of the SNOT-22 following elexacaftor/tezacaftor/ivacaftor (ETI) administration. METHODS: Data from three prospective observational cohort studies investigating the impact of ETI on CF-CRS were pooled across four U.S. centers and used for validity assessments. SNOT-22 scores, Lund-Mackay (LM) computed tomography (CT) sinus scores, and Cystic Fibrosis Questionnaire-Revised (CFQ-R) scores were used to assess test-retest reliability, construct validity, and responsiveness to clinical change in SNOT-22 scores. RESULTS: Strong test-retest reliability was observed for the SNOT-22 during the first 6 months post-ETI (N = 53, all r ≥ 0.80, p < 0.001). SNOT-22 intraclass correlation coefficients were strong (0.883) at 3 and 6 months after ETI was initiated and moderate (0.693) across all time points. Mean individual scores in 20 SNOT-22 items decreased from baseline to post-ETI (90.1%, p < 0.05). Moderate convergent validity was observed between pre-treatment SNOT-22 scores and LM scores (r = -0.42, p = 0.002) and CFQ-R respiratory domain scores (r = -0.35, p = 0.025). CONCLUSIONS: The SNOT-22 is a valid, reliable, and responsive instrument for evaluating CRS-specific QOL in adults with CF, and functions effectively as a unidimensional construct across most of its 22 items.