CD40LG and Q fever: In a study by Beersma et al., 3 of the 12 serological kits for M. pneumoniae had false positivity for M. pneumoniae IgM in 4 Q fever controls (ImmunoCardTM [75%, 3/4], NovumTM [100%, 4/4], SeroMPTM [50%, 2/4]) [19].