A diagnostic score for anti-MAG neuropathy or CIDP in patients with anti-MAG antibody

Background: We developed a diagnostic score to discriminate anti-MAG neuropathy from chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and applied it to patients with atypical anti-MAG neuropathy. Methods: The clinical and electrophysiological features of patients with a diagnosis of typical anti-MAG neuropathy have been compared to those of patients with a diagnosis of CIDP. The association of each feature with the diagnosis was assessed in the two groups. Features showing a significant association with the diagnosis were included in a multivariable logistic regression model and adjusted odds ratios were estimated for each feature. A score ranging from 1 to 3 was applied to each feature based on the magnitude of the estimated odds ratios. The score was then applied to patients with a clinical diagnosis of CIDP who also had high anti-MAG antibody titers (CIDP-MAG). Results: We included 31 anti-MAG neuropathy patients, 45 typical CIDP patients, and 16 CIDP-MAG patients. Scores in anti-MAG antibody patients ranged from 1 to 5, while in CIDP patients ranged from -7 to -1. Using the score, 4/16 CIDP-MAG patients were diagnosed to have anti-MAG neuropathy and 12/16 patients to have CIDP. Response to intravenous immunoglobulin in the CIDP-MAG patients classified as CIDP was similar to that of definite CIDP patients and higher than that of anti-MAG neuropathy patients. Conclusions: Our score allowed to accurately discriminate, among patients with anti-MAG antibodies, those affected by CIDP from patients with anti-MAG neuropathy. This score may help choose proper treatment for patients with anti-MAG antibodies with a CIDP-like presentation.