Development and validation of the Pediatric Autoimmune encephalitis Severity Scale in children with autoimmune encephalitis.
AIM To develop the Pediatric Autoimmune encephalitis Severity Scale (PASS) using expert consensus and the Delphi process, and validate it in children with autoimmune encephalitis. METHOD This prospective observational study enrolled children who underwent serial rating with PASS, the Clinical Assessment Scale in Autoimmune Encephalitis (CASE), and the modified Rankin Scale, at eight time points until 6 months of presentation. Clinical outcomes included the Pediatric Quality of Life Inventory (PedsQL) score (parent-rated) and developmental and intellectual outcome at 6 months. Interrater agreement, internal consistency, and correlations of PASS and CASE with clinical outcomes were compared. RESULTS There were 361 assessments in 27 children (11 females, 16 males) with autoimmune encephalitis (15 with antibody-negative autoimmune encephalitis, 11 with N-methyl-D-aspartate receptor antibody encephalitis, and one with steroid-responsive encephalopathy associated with autoimmune thyroiditis) with a median age at onset of 4 years (interquartile range = 3 years to 6 years 5 months). There was excellent interrater agreement for PASS and CASE with comparable intraclass correlation coefficients (0.984 vs 0.983). The worst PASS score was inversely correlated with the final PedsQL score (r = -0.42, p = 0.047). Factor analysis revealed distinct 'cognitive and behavioural' and 'disinhibition and excitability' dimensions in the PASS items. INTERPRETATION PASS is a severity assessment tool for autoimmune encephalitis in children and offers an alternative to adult scales, which may be difficult to use in children.