A new Patient-Reported Outcome Scale to assess autoimmune Encephalitis: PROSE.

Abstract

Autoimmune encephalitis (AIE) has long-lasting effects. Generic clinical assessment-scales insufficiently capture disease-specific sequelae. Patient-reported outcome measures (PROMs) assess outcomes important to patients, ensuring relevance in the clinic and trials. We developed a disease-specific patient-reported outcome scale for encephalitis (PROSE). Existing PROM-items (n = 235) were evaluated for content-validity and supplemented with focus-group-derived items. Patients with a history of anti-NMDAR, anti-LGI1, or anti-CASPR2 encephalitis completed the preliminary item pool (n = 166). To refine and reduce the item-pool and create the PROSE, we conducted item-, factor-, and Rasch-analyses. Test-retest reliability was assessed over 2 weeks and convergent-validity against established measures. The analysis included data from 202 patients with anti-LGI1 (n = 97), anti-NMDAR (n = 85), and anti-CASPR2 (n = 20) encephalitis, median 3.5 years from diagnosis (range = 0.05-14; n = 41 <1 year). Prospective, repeated assessments (n = 52) were available in 22 patients diagnosed <24 months prior. Analyses supported the viability of a 40-item unidimensional interval scale for patient-perceived disease-severity: the PROSE. The person-separation (Cronbach's alpha = 0.92, p < 0.001) and test-retest reliability (intra-class correlation-coefficient = 0.93, p < 0.001, n = 23) were high. PROSE covers cognition, behavior, emotional and physical wellbeing, daily activities, and participation. PROSE scores were normally distributed and informative across subtypes and demographic groups, correlated with time-since-diagnosis (R = -0.32, p = 0.00018) and captured improvement over time prospectively (n = 22). They showed reasonable-to-good agreement with self-reported physical and emotional wellbeing (R = 0.57 and 0.55, p < 0.001) and quality of life (R = 0.57, p < 0.001) on Visual Analogue Scales, to existing PROMs (ρ = 0.42 to ρ = 0.81) and functional scores (mRS ρ = 0.44, p < 0.001, CASE ρ = 0.40, p < 0.001), with strongest correlations to aggregate constructs. PROSE is a psychometrically robust, disease-specific patient-reported outcome assessment-tool for encephalitis. ANN NEUROL 2026.