IngentaConnect Contact tracing using a new T-cell-based test: better correlation...

Authors: Zellweger, J-P.¹; Zellweger, A.²; Ansermet, S.²; de Senarclens, B.³; Wrighton-Smith, P.⁴

Source: The International Journal of Tuberculosis and Lung Disease, Volume 9, Number 11, November 2005 , pp. 1242-1247(6)

Publisher: International Union Against Tuberculosis and Lung Disease

Abstract:

SETTING: Residential institution for alcoholics in Switzerland.

OBJECTIVE: To compare the results of the tuberculin skin test (TST) and the new T-cell-based test for tuberculosis infection (T-SPOT™.TB) in subjects exposed to a case of smear-positive pulmonary TB (PTB).

DESIGN: After the notification of smear-positive PTB in a resident of an institution for alcoholics, contacts underwent TST and determination of Mycobacterium tuberculosis specific T-cells in blood by T-SPOT.TB. Results were analysed according to age, history of BCG vaccination, and level of exposure to the index case.

RESULTS: There was no correlation between the level of exposure and the TST results, but the T-SPOT.TB results were significantly correlated with the level of exposure (P = 0.029, OR 5.00, 95%CI 1.05–23.86). Contacts who had been previously BCG-vaccinated were significantly more likely to have a positive TST than unvaccinated contacts (52% vs. 0%, P = 0.0003), but there was no influence of prior BCG vaccination on T-SPOT.TB results.

CONCLUSIONS: T-SPOT.TB test results correlated better than TST with level of exposure to M. tuberculosis and were not confounded by prior BCG vaccination. This test allows better selection of contacts who should receive treatment for latent TB infection.

Keywords: tuberculosis; contact tracing; ELISPOT; IFN-γ release; tuberculin skin test

Document Type: Regular paper

Affiliations: 1: TB Dispensary, University Medical Policlinic, Lausanne, Switzerland 2: BBR-LTC Laboratories, Lausanne, Switzerland 3: Fondation ‘Les Oliviers’, Le Mont-sur-Lausanne, Switzerland 4: Oxford Immunotec, Oxford, United Kingdom

Contact tracing using a new T-cell-based test: better correlation with tuberculosis exposure than the tuberculin skin test