Ilyich, Irina

Abstract Objective Perimenopause is an under-recognized transition poorly measured by existing tools, which often overlook symptoms characteristic of this phase. To address this, we developed and validated the Perimenopause Symptom Scale (Peri-SS): a concise, phase-specific, psychometrically robust instrument for digital self-assessment and research use among U.S. women aged 35-59 who self-reported in perimenopause. Methods We conducted a longitudinal validation study with 1,255 U.S. women aged 35-59 (633 identified as perimenopausal) recruited via Prolific. Participants completed the Peri-SS, Menopause Rating Scale (MRS), and EuroQol 5-Dimension, 5-Level (EQ-5D-5L) at baseline and 7-14 days later. Following COSMIN guidelines, we assessed structural validity, internal consistency, test-retest reliability, criterion and construct validity, and responsiveness to change. Results The Peri-SS demonstrated strong psychometric performance. Confirmatory factor analysis confirmed a four-domain structure (vasomotor, psychological, sexual, physical), with excellent model fit (CFI = 0.932, RMSEA = 0.069). Internal consistency was excellent (α = 0.90 overall; domain range 0.73-0.86), and test-retest reliability was high (ICC = 0.82). Criterion validity was strong, with Peri-SS scores highly correlated with MRS (r = 0.88). Construct validity was supported through moderate correlations with EQ-5D-5L utilities (ρ = -0.50) and effective discrimination between groups by age, menopausal status, and hormone therapy use. The scale was also responsive to symptom changes over time (η² = 0.277). Conclusions The Peri-SS is a reliable, valid, responsive tool for assessing perimenopausal symptom burden. Its concise format and strong psychometric performance make it well-suited for research, clinical care, and digital health applications. Two sentence summary The Perimenopause Symptom Scale (Peri-SS) is a novel 16-item instrument developed to measure symptom burden during perimenopause across four domains. In a validation study among U.S. women aged 35-59 years, the Peri-SS demonstrated strong reliability, validity, and responsiveness, supporting its use in research, clinical care, and digital health settings.