CD40LG and erythema multiforme: Among late EM cases (>30 days), using the C6 ELISA or anti-Borrelia ELISA IgG plus VlsE/IgM as the first-tier test, the use of the EUROLINE-RN-AT IgG immunoblot led to the detection of twice as many cases as with the WB IgG (62.5% vs. 31.3%) with only a minimal difference in specificity (95.1% vs. 97.6%).