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.