• Paola Mantegani, Federica Piana, Luigi Codecasa, Laura Galli, Paolo Scarpellini, Adriano Lazzarin, Daniela Cirillo, and Claudio Fortis.
• Clinic of Infectious Diseases, San Raffaele Scientific Institute, Via Stamira D'Ancona 20, 20127, Milano, Italy.
• Clin Med Res. 2006 Dec 1; 4 (4): 266-72.

ObjectiveTo compare a RD1-based in-house ELISPOT-interferon-gamma (IFN-gamma) assay with a commercial (T-SPOT.TB) assay for the diagnosis of Mycobacterium tuberculosis (TB) infection and the efficacy of the tuberculin skin test (TST) and ELISPOT assay in detecting latent TB infection (LTBI).DesignEighty-six subjects (65 household contacts of contagious TB-infected patients, 13 subjects with active or previous TB infection, and 8 with suspected TB infection) were consecutively recruited in the context of a surveillance program.MethodsEnrolled subjects underwent the Mantoux TST and two different ELISPOT-IFN-gamma assays: an in-house assay using a pool of selected M. tuberculosis peptides (MTP) and the commercial T-SPOT.TB assay.ResultsThe in-house and commercial ELISPOT-IFN-gamma assays showed almost complete concordance (99%) in diagnosing acute or LTBI. When comparing the efficacy of the TST with the in-house ELISPOT assay in detecting TB infection, a small agreement was observed (k=0.344, P<0.0001): 36% of the subjects with a positive TST were ELISPOT-MTP negative and 12% with a negative TST were ELISPOT-MTP positive. Furthermore, 78% of the ELISPOT-MTP negative individuals were ELISPOT- Bacillus Calmette-Guérin (BCG) positive, most of whom had received BCG vaccination.ConclusionOur in-house ELISPOT assay based on a restricted pool of highly selected peptides is equivalent to the commercial T-SPOT.TB assay, is cheaper and is probably not confounded, unlike the TST, by BCG vaccination in our setting.

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