Comparative studies of two potency tests for antirabies serum: neutralization test in mice (MNT) and rapid fluorescent focus inhibition test (RFFIT).

At our institute the mouse neutralization test (MNT) was replaced by the rapid fluorescent focus inhibition test (RFFIT). Therefore, RFFIT results were statistically analyzed for their percentage limits at the 95% confidence level and were compared with those of the MNT. An anti-rabies immunoglobulin of human origin and the WHO standard serum were assayed on 20 consecutive days to determine the reproducibility of the RFFIT. Sera of 60 vaccinees were assayed for rabies antibodies by the RFFIT and MNT. The titers as well as the international units per ml showed a correlation of 0.95 and 0.87 respectively. In accordance with previous publications by other authors it was found that the RFFIT is a significantly better reproducticible test system than the MNT and excellently correlates with the latter method.