Cross-reactions were shown in a validation study conducted by Trombert-Paolantoni et al., where one of 15 sera from patients with Influenza, 6/16 with Syphilis, 2/17 infected with EBV and 2/13 patients with Borreliosis reacted with a false positive result in the same IgM ELISA[37]. Here, CD40LG is linked to syphilis.