An indirect immunoreaction is proposed to demonstrate anti-Borrelia antibodies in the serum of patients with
Lyme disease (LD). The binding of specific IgG antibodies to dried smears of Borrelia antigen (strain Ip21) without fixation is visualized by subsequent incubation with peroxidase-conjugated antibodies to human IgG, followed by incubation with H2O2 and 3,3-diaminobenzidine tetrahydrochloride as a chromogenic substrate. This test is easy-to-perform and readable by a simple routine light microscope. It requires no special devices (a fluorescence microscope, a photometer, etc.) and may read data within days without any changes. The preliminary data on 59 sera from patients with various clinical symptoms of LD, as well as on leptospirosis, toxoplasmosis, and syphilis positive patients’ sera showed a good fit of the immunoperoxidase slide test (IPT) with the indirect immunofluorescence test. In view of this fact, the IPT is promising as a simple screening assay for large-scale serological surveys for BL.