title: Interferon-gamma-release assays detect recent tuberculosis re-infection in elderly contacts.
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.
authors.affiliation: Section of Respiratory Disease, Department of Oncology, Hematology and Respiratory Disease, University of Modena, and Policlinico Hospital of Modena, Modena, Italy. giovanni.ferrara@unipg.it
authors.forename: G
authors.initials: G
authors.lastname: Ferrara
authors.forename: M
authors.initials: M
authors.lastname: Losi
authors.forename: R
authors.initials: R
authors.lastname: D'Amico
authors.forename: R
authors.initials: R
authors.lastname: Cagarelli
authors.forename: A M
authors.initials: AM
authors.lastname: Pezzi
authors.forename: M
authors.initials: M
authors.lastname: Meacci
authors.forename: B
authors.initials: B
authors.lastname: Meccugni
authors.forename: I
authors.initials: I
authors.lastname: Marchetti Dori
authors.forename: F
authors.initials: F
authors.lastname: Rumpianesi
authors.forename: P
authors.initials: P
authors.lastname: Roversi
authors.forename: L
authors.initials: L
authors.lastname: Casali
authors.forename: L M
authors.initials: LM
authors.lastname: Fabbri
authors.forename: L
authors.initials: L
authors.lastname: Richeldi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002478:Cells, Cultured; D016358:Contact Tracing; D004196:Disease Outbreaks / Q000517:prevention & control*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006707:Homes for the Aged; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009735:Nursing Homes; D011237:Predictive Value of Tests; D012008:Recurrence; D013601:T-Lymphocytes / Q000276:immunology* / Q000382:microbiology; D013997:Time Factors; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology / Q000635:transmission
chemical_list: D007371:Interferon-gamma