Serum

Preferred Minimum: 2.0 mL serum
Absolute Minimum: 0.5 mL serum

3-4 weeks upon receipt at reference laboratory

Reportable range is 0.1 to 15.0 IU/mL
Less than 0.1 IU/mL: Below detection limit

In humans a results of 0.5 IU/mL or higher is considered an acceptable response to rabies vaccination according to the World Health Organization (WHO) guidelines.

Quantitative results. For those who want to know their exact titer between the reportable range.

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. The antibodies are called rabies virus neutralizing antibodies (RVNA).

This test is only intended for vaccine response, not for diagnosis of infection.

In RFFIT, your serum (the non-cellular portion of your blood) is first diluted fivefold (1part serum in 4 parts diluent). Further (serial fivefold) dilutions are performed, each of which contain less and less of your 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, some tissue culture 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 antibody in your serum), 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.

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