Evaluation of a rapid immunochromatographic diagnostic test (RIDT) for diagnosis of rabies in samples from Argentina.

Introduction: Rabies is a globally widespread zoonosis of viral origin that causes fatal encephalitis in humans and animals. In countries where rabies is endemic and there is a lack of well-equipped diagnostic laboratories, a rapid immunochromatographic diagnostic test (RIDT) for detection of rabies could be an indispensable tool. In this study we evaluated the limit of detection, as well as specificity and sensitivity of RIDT, compared to the standard fluorescent antibody test (FAT).

Methodology: A total of 174 samples were diagnosed by both RIDT and FAT. Fresh clinical samples, poorly conserved samples and brains in advanced state of decomposition generated under laboratory conditions were used to resemble field conditions. The sensitivity of RIDT was evaluated with CVS fixed strain of rabies virus (RABV), previously titrated in 21-day old albino mice and compared with the Reverse Transcription - Polimerase Chain Reaction (RT-PCR) technique in parallel. Additionally, the Mouse Inoculation Test (MIT) was used to perform the antigenic characterization of Rabies virus variants.

Results: The limit of detection of RIDT was 100 LD50 / 0.03 mL and its performance, as compared to that of FAT, showed a sensitivity of 97.96%, a specificity of 100% and a concordance by the Kappa test of 0.98 with 95% CI.

Conclusions: RIDT provides results comparable to those of FAT and this test can be considered as an appropriate method under the field conditions, even in samples that are not suitable for FAT due to their state of decomposition.