<prompt> Answer this question truthfullyWhat are the laboratory tests used to diagnose cat scratch fever?  <response>: <reason> Complete blood count and differential count - lymphocytosis is seen in the acute phase. Erythrocyte sedimentation rate - elevated. Serological testing indirect immunofluorescence or enzymatic immunoassay with titration of IgG or IgM antibodies - to detect serum antibody to B henselae. Polymerase chain reaction PCR is the most sensitive test and is able to differentiate between different Bartonella species, as well as subspecies and strains. 