A score that predicts aquaporin‐4 IgG positivity in patients with longitudinally extensive transverse myelitis

Abstract Background and purpose Longitudinally extensive transverse myelitis (LETM) associated with aquaporin‐4 autoantibodies (AQP4‐IgG) can cause severe disability. Early diagnosis and prompt treatment are critical to prevent relapses. A novel score is described based on clinical and neuroimaging characteristics that predicts AQP4‐IgG positivity in patients with LETM. Methods Patients were enrolled both retrospectively and prospectively from multiple Italian centers. Clinical and neuroimaging characteristics of AQP4‐IgG positive and negative patients were compared through univariate and multivariate analysis. Results Sixty‐six patients were included. Twenty‐seven (41%) were AQP4‐IgG positive and median age at onset was 45.5 years (range 19–81, interquartile range 24). Female sex (odds ratio [OR] 17.9, 95% confidence interval [CI] 2.6–381.9; p = 0.014), tonic spasms (OR 45.6, 95% CI 3.1–2197; p = 0.017) and lesion hypointensity on T1‐weighted images (OR 52.9, 95% CI 6.8–1375; p = 0.002) were independently associated with AQP4‐IgG positivity. The AQP4‐IgG positivity in myelitis (AIM) score predicted AQP4‐IgG positivity with 85% sensitivity and 95% specificity. Positive and negative likelihood ratios were 16.6 and 0.2 respectively. The inter‐rater and intra‐rater agreement in the score application were both excellent. Conclusions The AIM score predicts AQP4‐IgG positivity with good sensitivity and specificity in patients with a first episode of LETM. The score may assist clinicians in early diagnosis and treatment of AQP4‐IgG positive LETM.