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

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.

Automated summary

This article describes a novel scoring method based on clinical and neuroimaging characteristics that predicts AQP4-IgG positivity in patients with LETM. The score has good sensitivity and specificity, which can assist clinicians in the early diagnosis and treatment of AQP4-IgG positive LETM.