Quantitative analysis of aquaporin-4 antibody in longitudinally extensive transverse myelitis.

Aquaporin-4 (AQP-4) antibody-positive longitudinally extensive transverse myelitis (LETM) is referred to as a neuromyelitis optica (NMO) spectrum disorder. We conducted an exploratory investigation of correlations between AQP-4 antibody serum levels, as determined by a fluorescent immunoprecipitation assay, and clinical characteristics in LETM. Expanded Disability Status Scores (EDSS) scores and number of segments of spinal cord involved were positively correlated to AQP-4 antibody levels. However, serum AQP-4 antibody levels were not correlated with the time to next attack or the conversion time of LETM to NMO, although seropositive LETM patients demonstrated a high conversion rate to NMO (78.1%).