Comparison of tuberculin skin test and a specific T-cell-based test, T-Spot™.TB, for the diagnosis of latent tuberculosis infection

There is substantial evidence that the detection of T cells specific for the proteins ESAT-6 and CFP-10 using the ex vivo enzyme-linked immunospot technique is a marked improvement on the existing tuberculin skin test (TST). This new technique, which detects,gamma-interferon-producing T cells, is now available as the commercial assay, T-Spot (TM).TB. We compared the T-Spot (TM).TB test with the TST for the diagnosis of latent tuberculosis infection (LTBI) in different groups of subjects. Significant accordance (85.7%) between the tests was found in subjects with active lung tuberculosis and in tuberculosis clinic and laboratory personnel (63.6%) but accordance was lowest and not significant amongst house contacts of tuberculosis patients (53.6%). We conclude that, in countries where vaccination is routinely performed, the T-Spot (TM).TB test is a useful diagnostic test for LTBI in highrisk groups when carried out either together with the TST and/or to confirm the TST result.