RFFIT Tests
About the RFFIT Test
Current Turnaround Time: RFFIT test results are normally available in 3 to 4 weeks from the date that the sample is received here at the Kansas State University Rabies Laboratory.
RFFIT stands for Rapid Fluorescent Foci Inhibition Test. It is a serum neutralization (inhibition) test, which means it measures the ability of rabies specific antibodies to neutralize rabies virus and prevent the virus from infecting cells. These antibodies are called rabies virus neutralizing antibodies (RVNA).
In RFFIT, the serum (the non-cellular portion of blood) is first diluted fivefold (1 part serum in 4 parts diluent). Further (serial fivefold) dilutions are performed, each of which contain less and less serum. These serum dilutions are mixed with a standard amount of live rabies virus and incubated. Whatever RVNA is present will neutralize the virus. Next, cultured cells are added and the serum/virus/cells are incubated together. Whatever rabies virus is left (i.e., that which has not been neutralized by the RVNA), will infect the cells and this can be seen under the microscope through the use of specific staining. Calculation of the endpoint titer is made from the percent of virus infected cells observed on the slide.
We provide both the World Health Organization (WHO) guideline of 0.5 International Units per milliliter (IU/mL) as an adequate response to rabies vaccination, as well as the ACIP level of “complete neutralization at a serum dilution of 1:5 in the RFFIT test” as evidence of adequate response in a person on our RFFIT antibody test reports. We provide both guidelines to better assist individuals and healthcare providers in their decision-making about how to interpret our tests results in light of vaccination status and the possible necessity of booster vaccination(s).
Prospective Serological Monitoring
For Prospective Serological Monitoring (PSM) per the Compendium for Animal Rabies Prevention and Control recommendations to evaluate a rabies exposed dog or cat for previous rabies vaccination, contact the laboratory directly (785)532-4483 or at rabies @vet.k-state.edu for sample submission information and form.