The Bartonella FISH assay is designed for qualitative detection of ribosomal RNA of bacteria belonging to the Genus Bartonella. The FISH test provides a significant increase in specificity over standard gram stain for the presence of Bartonella in a whole blood smear. A positive result indicates the presence of bacterium from the Genus Bartonella, including B. berkhoffii, B. henselae, B. elizabethae, B. quintana, or B. vinsonii. This test is unavailable for patients over 65 when ordered through physician services.