The Enferplex Bovine TB antibody test is a serological assay (identifies the presence of antibody) for bovine Tuberculosis (bTB). The test detects the presence of antibodies within blood to bovine tuberculosis by use of individual antigens. There are eleven different antigens used in the test and these are placed separately as individual spots within a well. If antibody to bTB is present in the blood sample being tested, then it will bind with the relevant antigen and the resultant reaction produces a chemiluminescent reaction, the light from which can be measured and quantified (see Figure 1 ).
Images from three individual testing wells showing individual antigen spots that have bound antibody and are luminescent. This light is measured to produce a quantitative result.
Thresholds are set for each individual antigen and if the level of Relative Light Units (RLU) is above this threshold, a positive reaction is deemed to have occurred. A positive test result is when two or more antigens are shown to be above the thresholds set for the antigens. There are two different thresholds set for each antigen, a high sensitivity setting and a high specificity setting, with the high specificity setting requiring a higher threshold to be reached for a positive reaction .
The timing of sampling after a tuberculin test (SICCT) significantly affects the sensitivity of detection of antibody. Samples taken approximately 10-30 days post—SICCT will benefit from an antibody ‘boosting’ effect due to an anamnestic response to PPD antigens in animals infected with bTB. Samples taken outside this ‘window’ (non-boosted) will have lower levels of antibody and the test will be less sensitive.