An evaluation of immunofluorescence and PCR methods for detection of rabies in archival carnoy-fixed, paraffin-embedded brain tissue

Direct immunofluorescence and PCR detection methods ere compared for sensit ivity in evaluating the rabies status of archival specimens of Carnoy-fixed , paraffin-embedded brain tissue. The material consisted of 23 samples obta ined during a rabies outbreak in Finland in 1988, and one sample isolated f rom a bat researcher who died of rabies in Finland in 1985. These results w ere compared with thr original diagnoses performed on the fresh tissues. Th e immunofluorescence assay detected 100%: (12/12) of the rabies-positive ar chival cases. A PCR assay designed to detect a 139-bp target near the 5' en d of the rabies nucleoprotein gene also detected 100% (12/17) of the sample s identified as positive in the fresh tissue specimens. A PCR assay designe d to detect a 304-bp target spanning the 139-bp target of the first assay d etected only 67% (8/12) of the original cases. No false positives were reco rded. Both immunofluorescence detection of antigen and PCR detection of a s hort region of the nucleoprotein gene are useful in determining the rabies status of fixed, paraffin-embedded (archival) material.