High Sensitivity of the BioNote Anigen Rapid Rabies Antigen Test in Detection of Diverse Rabies Virus Variants Suggests Utility for Global Rabies Control

Point-of-care, immunochromatographic tests have not reliably detected rabies virus and have not utilized a consistent diagnostic protocol. International diagnostic standards established by the World Organization for Animal Health require strategic and large-scale validation studies prior to widescale use. The United States (US) Centers for Disease Control and Prevention, National Rabies Reference Laboratory undertook a large-scale validation of the BioNote Anigen Rapid Rabies Antigen Test in collaboration with eight US public health laboratories and three international laboratories. Modifications were made to manufacturer instructions to maximize antigen concentration in the test diluent. A total of 1,399 samples underwent paired testing with one of three US gold standard tests, consisting of 31 types of animals and 9 rabies virus variants. Test sensitivity and specificity was 97.11% (CI: 95.21% - 98.27%) and 99.89% (CI: 99.36% - 99.98%). Fourteen samples resulted in false-negative results, primarily impacting dogs that were euthanized early or shown to have a low viral load. Limit of detection studies found that false-negative results often occurred when the sample had a PCR Ct value >23. The BioNote Anigen Test performed well across diverse RVVs found in North America. Sensitivity of the test was slightly lower than, but not statistically inferior to, the minimum 98% value established for the current gold-standard tests. This is the largest systematic evaluation of a rabies point-of-care test that includes diverse RVV and animal type and results suggest that the BioNote Anigen Test with the procedural changes would have broad benefits for rapid diagnosis in animals.