Tuberculosis IGRA

TB ELiFN

Test Attributes

• Specific antigens employed in the kit are identified only in MTB; not in BCG strains or other most non-tuberculous mycobacteria

• No cross-reactivity is found with other cytokines, e.g. IL-2 (40ng/ml), IL-4 (5ng/ml), IL-5, IL-6, IL-8, IL-10, IL12 (100ng/ml)

• No separation of T cells is required

• Sensitivity at 94.23% is reached with active TB patients

• Specificity at 96.23% is reached with healthy volunteers

• Measurement range of 0.15625 IU/ml to 10 IU/ml

• Stable for at least 12 months when stored at 2-8°C

• Components provided in ready-to-use format

Principle

This kit combines two principles, IGRA and ELISA, to measure the specific antigen mediated immune response. The antigens selected are present in Mycobacterium tuberculosis (MTB), but not bacille Calmette-Guerin (BCG) vaccine and most non-tuberculous mycobacteria. T cells in the whole blood from persons that have been infected with MTB will release IFN-γ when mixed with these specific antigens. The released IFN-γ is then quantitatively detected by a sandwich ELISA:

The IFN-γ which are present in the blood will bind onto the wells of a microtitre plate (strip) supplied pre-coated with capture antibody. The bound IFN-γ are detected by the detection antibody labelled by horseradish peroxidase (HRP), which in turn is visualised by adding TMB solution. Any coloured product is measured at 450 nm after adding stop solution. The quantity of bound HRP varies directly with the concentration of IFN-γ in the blood sample tested; thus, the absorbance, at 450 nm, is a measure of the concentration of IFN-γ in the test sample. The quantity of IFN-γ in the test sample can be calculated from the standard curve constructed from the standards, and corrected for sample dilution.

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