In patients with possible Bartonella henselae infection and elevated IgG titer, what is the best way to confirm the diagnosis: tissue biopsy with Warthin-Starry staining, tissue sent for Bartonella henselae PCR, or tissue sent for culture?  

First of all, it is important to only test people with a compatible clinical syndrome. If the syndrome is not that of babesia, then any positive tests are likely to be false positives. This is a basic testing principle. A very low pretest probability is likely to lead to false positive testing. The...