Tissot-Dupont et al. [81] recommend, as IFA cut-off values, titers of anti-phase II IgG of ≥200 and titers of anti-phase II IgM of ≥50 for the diagnosis of human acute Q fever, and titers of anti-phase I IgG ≥ 800 for the diagnosis of human chronic Q fever. This evidence concerns the gene CD40LG and Q fever.