Objectives: To determine threshold titers and diagnostic accuracy of anti-GM1 and anti-sulfatide antibodies (Ab) for autoimmune polyneuropathies (PN) in overall and for particular subtypes of them.
Materials and methods: In this study 84 PN patients, 120 epileptics and 93 healthy controls' sera were tested by enzyme-linked immunosorbent assay for autoAbs and results confirmed by thin-layer chromatography. Frequencies of positive patients at increasing cut-off were compared to determine threshold titers. Accuracy was determined by Receiver Operator Characteristic analysis.
Results: A 1:2,000 titer for IgM anti-GM1 and a 1:4,000 titer for IgM anti-sulfatide Ab resulted to be threshold titers for autoimmune PN in overall. IgM anti-GM1 and anti-sulfatide Ab had low discriminating capacity between autoimmune PN and other PN, but good discriminating capacity between motor neuropathy (for anti-GM1 Ab) or PN in IgM-paraproteinemia or chronic painful sensory axonal PN (for anti-sulfatide Ab) and other PN.
Conclusion: Our results suggest that testing IgM anti-GM1 or anti-sulfatide Ab is useful only for diagnostic confirmation of specific subtypes of autoimmune PN.