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Journal of Clinical Microbiology, June 2006, p. 1944-1950, Vol. 44, No. 6
0095-1137/06/$08.00+0     doi:10.1128/JCM.02265-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

An In-House RD1-Based Enzyme-Linked Immunospot-Gamma Interferon Assay Instead of the Tuberculin Skin Test for Diagnosis of Latent Mycobacterium tuberculosis Infection

Luigi Codecasa,1 Paola Mantegani,2 Laura Galli,2 Adriano Lazzarin,2,3 Paolo Scarpellini,2 and Claudio Fortis2*

Villa Marelli Institute, Lombardy Regional Reference Centre for Tuberculosis, Niguarda Hospital, Milan, Italy,1 Clinic of Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy,2 "Vita-Salute" San Raffaele University, Milan, Italy3

Received 28 October 2005/ Returned for modification 15 December 2005/ Accepted 17 March 2006

Identification of individuals infected with Mycobacterium tuberculosis is essential for the control of tuberculosis (TB). The specificity of the currently used tuberculin skin test (TST) is poor because of the broad antigenic cross-reactivity of purified protein derivative (PPD) with BCG vaccine strains and environmental mycobacteria. Both ESAT-6 and CFP-10, two secretory proteins that are highly specific for M. tuberculosis complex, elicit strong T-cell responses in subjects with TB. Using an enzyme-linked immunospot (ELISPOT)-IFN-{gamma} assay and a restricted pool of peptides derived from ESAT-6 and CFP-10, we have previously demonstrated a high degree of specificity and sensitivity of the test for the diagnosis of TB. Here, 119 contacts of individuals with contagious TB who underwent TST and the ELISPOT-IFN-{gamma} assay were consecutively recruited. We compared the efficacy of the two tests in detecting latent TB infection and defined a more appropriate TST cutoff point. There was little agreement between the tests (k = 0.33, P < 0.0001): 53% of the contacts with a positive TST were ELISPOT negative, and 7% with a negative TST were ELISPOT positive. Furthermore, respectively 76 and 59% of the ELISPOT-negative contacts responded in vitro to BCG and PPD, suggesting that most of them were BCG vaccinated or infected with nontuberculous mycobacteria. The number of spot-forming cells significantly correlated with TST induration (P < 0.0001). Our in-house ELISPOT assay based on a restricted pool of highly selected peptides is more accurate than TST for identifying individuals with latent TB infection and could improve chemoprophylaxis for the control of TB.


* Corresponding author. Mailing address: Clinic of Infectious Diseases, San Raffaele Scientific Institute, Via Stamira D'Ancona 20, 20127 Milano, Italy. Phone: 39 02 26437964. Fax: 39 02 26437989. E-mail: fortis.claudio{at}hsr.it.


Journal of Clinical Microbiology, June 2006, p. 1944-1950, Vol. 44, No. 6
0095-1137/06/$08.00+0     doi:10.1128/JCM.02265-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.




This article has been cited by other articles:

  • Begg, D. J., de Silva, K., Bosward, K., Di Fiore, L., Taylor, D. L., Jungersen, G., Whittington, R. J. (2009). Enzyme-linked immunospot: an alternative method for the detection of interferon gamma in Johne's disease. jvdi 21: 187-196 [Abstract] [Full Text]  
  • Mantegani, P., Piana, F., Codecasa, L., Galli, L., Scarpellini, P., Lazzarin, A., Cirillo, D., Fortis, C. (2006). Comparison of an In-house and a Commercial RD1-based ELISPOT-IFN-{gamma} Assay for the Diagnosis of Mycobacterium tuberculosis Infection. Clin Med Res 4: 266-272 [Abstract] [Full Text]