Anti-ganglioside antibodies: experience from the Italian Association of Neuroimmunology external quality assessment scheme.

Background: Anti-ganglioside antibodies are currently used in the differential diagnosis of suspected immune-mediated neuropathies. In-house and increasingly used commercial assays seem to perform suboptimally, and comparative information on their analytical performance are essentially lacking. Born within the frame of guidelines and standardization activities by the Italian Association of Neuroimmunology, this external quality assessment scheme (EQAS) is a real-life snapshot of the laboratory diagnostics in this field. Methods: The EQAS consisted of five surplus, anonymized serum samples from patients with clinically-defined neuropathies and two serum samples from healthy blood donors. Eight laboratories used commercial line-/dot-blots, seven in-house/commercial ELISAs (in addition, 13 laboratories tested a recently released ELISA by Buhlmann). Only high anti-ganglioside antibody reactivities were considered, in accordance with consolidated recommendations. Results: Large variations in anti-ganglioside antibody profiles were observed, even, although to a lesser extent, within homogeneous classes of assays. Concordance between the profiles and clinical phenotypes was also partial. Conclusions: Although conducted on a relatively small, but representative number of Italian laboratories, this EQAS shows a critical between-laboratory disagreement in the test results of anti-ganglioside antibodies. Also considering the trend for using certified assays in generalist laboratories, strong efforts toward standardization and the identification of the best method(s) for their determinations are compellingly needed.