Psychometric Validation and Meaningful Change Thresholds of the New Nasal Polyposis Symptom Diary

OBJECTIVES The Nasal Polyposis Symptom Diary (NPSD) is a novel and short patient-reported outcome (PRO) tool specifically developed to assess important and relevant symptoms reported by patients with chronic rhinosinusitis with nasal polyposis (CRSwNP). We evaluated the psychometric properties of 4 predefined NPSD-derived scores intended to support symptom-improvement assessments of investigational therapies for inclusion in product labeling. METHODS Five hundred eighteen patients with severe CRSwNP from a Phase III clinical trial (NCT03401229) completed the NPSD, comprising 11 items: 8 symptom-specific, 2 symptom-impact, and 1 optional medication-compliance. The psychometric characteristics of 3 single-item symptom scores (Nasal Blockage Score [NBS], Nasal Congestion Score [NCS], and Difficulty with Sense of Smell Score [DSS]) and a Total Symptom Score (TSS, summary of the 8 symptom-specific items) were evaluated for reliability, validity, and ability to detect change. Within-patient meaningful change thresholds (MCTs) were established using anchor- and distribution-based methods. Comparative PROs included the 22-item Sino-Nasal Outcome Test (SNOT-22) and Patient Global Impression of Severity (PGI-S). RESULTS The TSS exhibited strong internal consistency (Cronbach α = .88) and test-retest reliability (intraclass correlation coefficient >.80). Correlation between the TSS and SNOT-22 total score indicated good convergent validity (r = .70). All 4 NPSD scores demonstrated known-groups validity (significant differences among subgroups of patients with predetermined disease severity levels based on PGI-S categories) and were sensitive to detect change in patients' clinical status (significant differences among subgroups of patients with reported changes between 2 time-points in PGI-S and Patient Global Impression of Change scores). MCTs for improvement were established at 1.0 point for NBS, NCS, and DSS, and 4.0 points for TSS. CONCLUSION These findings support the reliability, validity, and suitability of the 4 NPSD-derived scores for evaluating treatment effect on CRSwNP symptoms and their use in clinical trials with predetermined MCTs for improvement.