Anti-factor H autoantibodies assay.

Non-Shiga-toxin-associated hemolytic uremic syndrome (atypical HUS) is a rare form of thrombotic microangiopathy which associates hemolytic anemia, thrombocytopenia, and acute renal failure. In 10 % of cases the disease is linked to presence of autoantibodies directed against Factor H (FH), the main plasmatic alternative complement pathway regulatory protein. Their presence induces an acquired functional FH deficiency. The anti-FH autoantibodies screening must be performed at the very onset of the disease in all cases of HUS, in order, first, to make the proper diagnosis as early as possible, and second to support an appropriate therapy including early plasma exchanges and immunosuppressive treatments. Thus, anti-CFH IgG represents a diagnostic marker and the titer determination is useful for assessing disease evolution, because changes precede clinical symptoms, and for monitoring of treatment. Presence of anti-FH IgG has been recently reported to be associated with other clinical context such as C3 glomerulopathies, but their pathogenicity in these conditions remains to be assessed. Here we describe the ELISA assay allowing the detection of these autoantibodies and report the analysis which can be performed concomitantly to improve the diagnosis.