Tests can be divided into two categories:
1. Tests which detect the Borrelia organism directly
Borrelia burgdorferi is only transiently present in circulating blood and whole blood is not considered a useful diagnostic specimen for evaluation of infection. Spirochetes may reportedly be found in synovial fluid using dark-field microscopy, but low numbers of organisms are present in clinical specimens, precluding direct visualisation. Although organisms have been reportedly identified in peripheral blood, urine, joint and CSF fluids by use of dark-field or phase-contrast microscopy in naturally and experimentally infected dogs, these techniques are not generally used in clinical practice.
Cell culture isolation requires specialised media and is challenging because of the relatively low density of organisms present in chronic infections.
Polymerase chain reaction (PCR) based tests, which are more sensitive, are also available to detect the organism in tissue samples.
2. Tests which measure antibodies against Borrelia
These include the indirect fluorescent antibody (IFA) assay, enzyme-linked immunosorbent assay (ELISA), or characteristic serum proteins analysis (Western blot technique).
Serology is the mainstay for confirming a clinical impression of Lyme disease. However, asymptomatic dogs in endemic areas may often be seropositive. Another limitation is that animals can take some time to seroconvert following infection. Therefore, many early cases can return a negative result on serology. Animals may also remain seropositive for a long time following treatment, making it difficult to determine whether a successful resolution has been achieved.
Many veterinarians consider the specific C6-based assay to be the initial screening method of choice for evaluating a dog for exposure to, and potentially infection with, Borrelia burgdorferi.