Nichol's strain is used in:
Treponema pallidum immobilization (TPI) test, considered both as a qualitative and as a quantitative test, and then various specific aspects of passage of the Nichols strain of treponeme in rabbit testes. a serological test for syphilis in which a solution containing the living causative spirochete (Treponema pallidum) is combined with serum in the presence of complement with immobilization of the active spirochetes indicating a positive result
TP HA test
TPI test
VDRL
FTA-ABS