Table 2. Diagnostic grading system to judge the certainty of the correct diagnosis of TBRF.

Diagnostic method	Grade of diagnostic certainty	Case classification	Comment
PCR	A	Confirmed diagnosis	Highest level of evidence, detection even at low level of spirochetemia
Microscopy	B	Microscopic diagnosis	High level of evidence, easy to carry out, examiner-dependent, likelihood of detection depends on level of spirochetemia
Culture	B	Microscopic diagnosis	High level of evidence, difficult to carry out, time demanding
Animal inoculation	B	Microscopic diagnosis	High level of evidence, difficult to carry out, time demanding
Serology	C	Indirect evidence	Intermediate level of evidence, not standardized, cross-reaction with other Borrelia (e.g. Lyme disease) possible

PCR, polymerase chain reaction.