|Values are valid only on day of printing.|
The QuantiFERON-TB Gold In-Tube test utilizes peptide cocktail simulating ESAT-6, CFP-10, and TB7.7 proteins, which are used to stimulate T cells in whole heparinized blood during incubation. The test is performed in 2 stages. First, 1 mL of whole blood is collected into each of 3 collection tubes: Nil control tube, TB antigen tube, mitogen tube. Tubes are incubated at 37 degrees C within 16 hours of collection. Following a 16 to 24 hour incubation period, the tubes are centrifuged and the plasma is used to test for the amount of interferon-gamma (IFN-gamma) present, measured by enzyme-linked immunosorbent assay.
A test is considered positive for an IFN-gamma response to the TB antigen tube that is significantly above the negative control (Nil tube) value (IU/mL). The mitogen-stimulated plasma sample (mitogen tube) serves as an IFN-gamma positive control for each sample tested. A low response to mitogen (<0.5 IU/mL) is an indeterminate result when a blood sample also has a negative response to the TB antigens. This pattern may occur with insufficient lymphocytes, reduced lymphocyte activity due to prolonged specimen transport or improper specimen handling, or inability of the patient's lymphocytes to generate IFN-gamma. The negative (Nil) sample adjusts for background, heterophile antibody effects, or nonspecific IFN-gamma in blood samples. The IFN-gamma level of the negative control is subtracted from the IFN-gamma level for the TB antigen tube and mitogen tube.(Package insert: QuanitFERON-TB Gold [In-Tube Method], Cellestis Limited, Carnegie, Victoria, Australia, document number 05990301B, January 2007)
Note: Tuberculosis antigen IU/mL value is reported (TB Ag IU/mL Value). This information may be required for certain CDC reporting forms (eg, Form I-693).
Monday through Friday