What is the purpose of cell washing and counting in the T-SPOT.TB test?
Cell washing and counting are very important steps that improve the sensitivity and reliability of the T-SPOT.TB test. Cell washing removes the background interferon gamma (IFN-γ) that may otherwise produce interference in the test. Removal of this background IFN-γ provides a more reliable “signal”. This washing step is absent from ELISA methods. Cell counting corrects for those samples where the PBMC count is low (e.g. the immunocompromised). After washing, the PBMCs (Peripheral Blood Mononuclear Cells) are counted to ensure that 250,000 cells per well are used in the test.
