Qual Life Res. 2026 Jun 19;35(8):207. doi: 10.1007/s11136-026-04291-z.
ABSTRACT
PURPOSE: This study evaluated the measurement properties and ability to detect clinically meaningful change of the Mastocytosis Symptom Severity Daily Diary (MS2D2), a patient-reported outcome instrument designed to measure symptom severity in adults with nonadvanced systemic mastocytosis (NonAdvSM).
METHODS: Psychometric evaluation of the MS2D2 used blinded data from 230 adults with NonAdvSM enrolled in the Summit Phase 2 study (NCT05186753). The study comprised two parts: Part 1 (n = 54) for dose-finding and initial domain structure development, and Part 2 (n = 179) for efficacy evaluation, validation and longitudinal assessment. Analyses included item-level statistics, confirmatory factor analysis (CFA), internal consistency (Cronbach’s α), test-retest reliability (ICC), convergent and known-groups validity, responsiveness, and anchor-based estimation of meaningful change thresholds.
RESULTS: Structural validity supported a four-domain, 11-item Total Symptom Score (TSS) framework. Internal consistency and test-retest reliability were excellent (α = 0.79-0.95; ICC = 0.95-0.98). Convergent validity was supported through strong correlations with disease-specific symptom and health-related quality of life (HRQoL) measures (r = 0.85 and r = 0.59). Known-groups validation revealed domain scores differing by 2-5 points between anchor severity strata and TSS by 2.8 points (all p < 0.05). Scores were sensitive to change, correlating (r = 0.39-0.74) with changes in patient status. TSS within-patient meaningful improvement thresholds were 1.6-2.2 points (0-10 scale) and 17.2-24.7 points (0-110 sum), with domains showing similar ranges. Percent change thresholds indicated meaningful improvement at approximately 30-40% reduction for both TSS and domain scores.
CONCLUSIONS: MS2D2 is a reliable, valid, and responsive instrument for assessing symptom severity in NonAdvSM, with evidence supporting its use in clinical trials to evaluate treatment benefit.
PMID:42319518 | DOI:10.1007/s11136-026-04291-z
