Specificity of the agar gel microimmunodiffusion test in rabies diagnostics.

The agar-gel microimmunodiffusion test (MIDT) with commercially available antirabies sera from different sources was applied to evaluation of rabies infection at about 500 brains from suspected animals. The high nonspecificity of the test and false positive results with nonvirulent materials were stated when compared with the histopathological, biological and FA tests. For evaluation of the nonspecificity and its cause, different antirabies sera and brain antigens from noninfected and rabid animals were used. Absorption of sera with tissue powders or immuno absorbent had a little influence on test specificity. The main causes of nonspecificity was the presence of antibrain antibodies in sera of producers-animals hiperimmunized by brain and spinal cord tissue vaccines. Application of the test to rabies diagnostics without purified control antigens and highly specific sera seems to be unjustified.