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Updated: Jun 19, 2026

Application of Long-term cultured Interferon-γ Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle
Published on: July 11, 2015
Interferon-gamma-release assays detect recent tuberculosis re-infection in elderly contacts
1Section of Respiratory Disease, Department of Oncology, Hematology and Respiratory Disease, University of Modena, and Policlinico Hospital of Modena, Modena, Italy. giovanni.ferrara@unipg.it
Abstract:
The tuberculin skin test (TST) does not discriminate between recent and remote latent tuberculosis infection (LTBI). This study was carried out to test two interferon-gamma-based blood assays in recent contacts with high prevalence of remote LTBI. We performed a contact tracing investigation in a nursing home for the elderly, where elderly patients were exposed to a case of pulmonary tuberculosis. TST, QuantiFERON-TB Gold (QFT-G) and T-SPOT.TB (TS.TB) were performed 8 weeks after the end of potential exposure. IFN-gamma measurements were recorded and correlation with exposure was evaluated. Twenty-seven (37.5%), 32 (44.4%) and 16 (22.2%) subjects were TST, TS.TB and QFT-G positive, respectively; agreement between TS.TB and QFT-G was good among exposed subjects only (K=0.915, 0.218 in unexposed, p<0.001). When amounts of IFN-gamma were corrected for the number of producing T cells, specific IFN-gamma production was significantly different between exposed and unexposed individuals (16.75+/-5.40 vs 2.33+/-0.71 IFN-gamma IU/1000 SFC, p=0.0001). QFT-G and TS.TB provided discordant results among elderly contacts. Unlike TST, the specific IFN-gamma response might discriminate between recent and long-lasting tuberculosis infection.
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