Diagnosis of Bartonella infection, especially in the context of a cat scratch
This assay can be used as an aid to diagnose recent or past infection with Bartonella henselae or Bartonella quintana.
A positive immunofluorescence assay (IFA) IgM (titer >1:20) suggests a current infection with either Bartonella henselae or Bartonella quintana.
A positive IgG (titer >1:128) suggests a current or previous infection. Increases in IgG titers in serial specimens suggest active infection.
Normal serum specimens usually have an IgG titer of less than 1:128. However, 5% to 10% of healthy controls exhibit a B henselae and B quintana titer of 1:128. Sera from healthy volunteers rarely show titers of 1:256 or greater. IgM titers in normal serum are typically less than 1:20. IgM titers at 1:20 or greater have not been seen in the normal population.
Molecular testing of tissue for Bartonella species nucleic acid is recommended in cases of suspected endocarditis.