Two-tier Lyme testing begins with a crucial distinction: a positive Lyme screening test is not, by itself, a positive Lyme test. That distinction matters when syphilis is in the differential, because antibodies produced against Treponema pallidum can react with antigens used in some Lyme disease screening assays. Treating the screen as a diagnosis can lead a clinician to label a patient with syphilis as having Lyme disease.
