Interferon-gamma-release assays detect recent tuberculosis re-infection in elderly contacts.
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.
Ferrara
G
G
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
Losi
M
M
D'Amico
R
R
Cagarelli
R
R
Pezzi
A M
AM
Meacci
M
M
Meccugni
B
B
Marchetti Dori
I
I
Rumpianesi
F
F
Roversi
P
P
Casali
L
L
Fabbri
L M
LM
Richeldi
L
L
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
D007371:Interferon-gamma