Sensitivity Q fever: acute Q fever): 20-30% (IgG),75- 83% (IgM), chronic Q-fever: 100%, past Q fever: 48-63% Sensitivity Spotted MSF/murine typhus - 91-100% Specificity Q fever: 82-100% Specificity Spotted MSF/murine typhus: 79-98%. Here, CD40LG is linked to typhus.