A comparative study of direct fluorescent antibody, mouse inoculation, and tissue culture infection testing for rabies diagnoses

The laboratory diagnosis of rabies is of fundamental importance to the evaluation of suspected cases of rabies virus (RABV) infection. Confirmation of direct fluorescent antibody test (DFAT) results via viral isolation (VI) is recommended, and the mouse inoculation test (MIT) is being replaced by the rabies tissue culture infection (RTCIT) test for ethical reasons. We evaluated 6.514 results from central nervous system (CNS) samples of different animals analyzed at the Pasteur Institute between 2008 and 2016 using the DFAT, RTCIT and MIT techniques and evaluated their concordance, sensitivity, specificity, and accuracy indices. The DFAT technique presented the best sensitivity (93.58 %), specificity (95.90 %), and accuracy (95.67 %) results. The RTCIT values of sensitivity, specificity and accuracy (70.42 %, 86.16 % and 84.62 % respectively) were lower than those of DFAT. The concordance between RTCIT and DFAT was moderate, with a kappa quotient k = 0.341. The MIT values of sensitivity, specificity, and accuracy were 89.58 %, 100 % and 98.97 % respectively. The concordance between MIT and DFAT was substantial, with a k value of 0.720. DFAT, considered the “gold standard”, was effective in all animals except horses. Our analyses evidenced that DFAT presents satisfactory results, although RTCIT did not appear favorable as a confirmatory technique.