Utility of the IFN-g assays using Mycobacterium tuberculosis-specific antigens for the diagnosis of latent infection in contacts of people with sputum smear-positive pulmonary tuberculosis

Abstract number: 1732_312

De Souza Galvao M., Latorre I., Mila C., Jimenez M., Prat C., Altet N., Haba L., Perez M., Ruiz-Manzano J., Ausina V., Dominguez J.

Objective: To determinate IFN-g response by specific T cells with QuantiFERON-TB GOLD (QFN-TB GOLD) (Cellestis, Australia) and T-SPOT.TB (Oxford Immunotec, United Kingdom) in contacts of people with sputum smear-positive pulmonary tuberculosis.

Materials and Methods: We included 91 individuals enrolled in contact tracing studies after exposure to a sputum smear-positive pulmonary tuberculosis case. Blood samples and isolated peripheral blood isolated mononuclear cells were stimulated with M. tuberculosis-specific antigens ESAT-6 and CFP-10. We determined the IFN-g production in whole-blood supernatants samples by EIA with the QFN-TB GOLD assay and in mononuclear cells by ELISPOT with the T-SPOT.TB assay. Both IFN-g tests were performed according to the manufacturer's instructions. Tuberculin skin test (TST) was administered by the Mantoux method using two tuberculin units of PPD RT23 (Statens Serum Institut, Denmark). Induration was measured after 48–72 h. Indurations higher than 5 mm were considered positive.

Results: We included 91 individuals with a exposure higher to 6 h/day, 62 of them with BCG vaccination scar. The percentage of positive results for TST, T-SPOT.TB and QFN-TB GOLD, in non-vaccinated and vaccinated individuals were the following: 71.4% and 94.9%; 70.4% and 47.3%; and 57.7% and 40.3%, respectively. The overall concordance between T-SPOT.TB and QFN-TB GOLD was higher (k = 0.632). Between vaccinated individuals that initiate a prophylaxis treatment, T-SPOT.TB was negative in 45.7% of cases, and QFN-TB GOLD in 59.2%.

Conclusions: (1) Both in vitro assays seem to have lower interference results with the BCG vaccination than TST, which suggest a higher specificity for QFN-TB GOLD and T-SPOT.TB assays. (2) Utilisation of these tests can help to reduce the number of unnecessary prophylaxes.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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