Rapid identification of Mycobacterium tuberculosis infection

The conventional intradermal tuberculin skin test (Mantoux test) is poorly specific and has unknown sensitivity for latent Mycobacterium tuberculosis infection. Two new tests offer the promise of improved tuberculosis diagnosis: the QuantiFERON(TM)-TB Gold test, based on a whole blood ELISA, and the T-SPOT(TM).TB test, based on the ex-vivo enzyme-linked immunospot (ELISpot) assay. These tests are more rapid and offer greater specificity and objectivity than the tuberculin skin tests, and the latter may also offer greater sensitivity. Both tests have yet to be validated in immunosuppressed patients. Available evidence suggests that these techniques will be feasible to apply within tuberculosis control programmes. Ongoing research priorities include head-to-head comparisons, validation in immunosuppressed populations, and longitudinal assessment of the predictive value of a positive blood test in latent infection for progression to active disease.