Performance of tests for latent tuberculosis in different groups of immunocompromised patients.
BACKGROUND
Immunocompromised persons infected with Mycobacterium tuberculosis (MTB) have increased risk of tuberculosis (TB) reactivation, but their management is hampered by the occurrence of false-negative results of the tuberculin skin test (TST). The T-cell interferon (IFN)-gamma release blood assays T-SPOT.TB (TS.TB) [Oxford Immunotec; Abingdon, UK] and QuantiFERON-TB Gold In-Tube (QFT-IT) [Cellestis Ltd; Carnegie, VIC, Australia] might improve diagnostic accuracy for latent TB infection (LTBI) in high-risk persons, although their performance in different groups of immunocompromised patients is largely unknown.


RESULTS
Over a 1-year period, we prospectively enrolled patients in three different immunosuppressed groups, as follows: 120 liver transplantation candidates (LTCs); 116 chronically HIV-infected persons; and 95 patients with hematologic malignancies (HMs). TST, TS.TB, and QFT-IT were simultaneously performed, their results were compared, and intertest agreement was evaluated. Overall, TST provided fewer positive results (10.9%) than TS.TB (18.4%; p < 0.001) and QFT-IT (15.1%; p = 0.033). Significantly fewer HIV-infected individuals had at least one positive test (9.5%) compared with LTCs (35.8%; p < 0.001) and patients with HMs (29.5%; p < 0.001). Diagnostic agreement between tests was moderate (kappa = 0.40 to 0.65) and decreased in the HIV-infected group when the results of the TS.TB were compared with either TST (kappa = 0.16) or QFT-IT (kappa = 0.19). Indeterminate blood test results due to low positive control values were significantly more frequent with QFT-IT (7.2%) than with TS.TB (0.6%; p < 0.001).


CONCLUSIONS
Blood tests identified significantly more patients as being infected with MTB than TST, although diagnostic agreement varied across groups. Based on these results, we recommend tailoring application of the new blood IFN-gamma assays for LTBI in different high-risk groups and advise caution in their current use in immunosuppressed patients.
Richeldi
Luca
L
University of Modena and Reggio Emilia, Modena, Italy. Electronic address: luca.richeldi@unimore.it.
Losi
Monica
M
University of Modena and Reggio Emilia, Modena, Italy.
D'Amico
Roberto
R
University of Modena and Reggio Emilia, Modena, Italy.
Luppi
Mario
M
University of Modena and Reggio Emilia, Modena, Italy.
Ferrari
Angela
A
University of Modena and Reggio Emilia, Modena, Italy.
Mussini
Cristina
C
University of Modena and Reggio Emilia, Modena, Italy.
Codeluppi
Mauro
M
University of Modena and Reggio Emilia, Modena, Italy.
Cocchi
Stefania
S
University of Modena and Reggio Emilia, Modena, Italy.
Prati
Francesca
F
University of Modena and Reggio Emilia, Modena, Italy.
Paci
Valentina
V
University of Modena and Reggio Emilia, Modena, Italy.
Meacci
Marisa
M
Policlinico Hospital, Modena, Italy.
Meccugni
Barbara
B
Policlinico Hospital, Modena, Italy.
Rumpianesi
Fabio
F
Policlinico Hospital, Modena, Italy.
Roversi
Pietro
P
University of Modena and Reggio Emilia, Modena, Italy.
Cerri
Stefania
S
University of Modena and Reggio Emilia, Modena, Italy.
Luppi
Fabrizio
F
University of Modena and Reggio Emilia, Modena, Italy.
Ferrara
Giovanni
G
University of Modena and Reggio Emilia, Modena, Italy.
Latorre
Irene
I
University of Modena and Reggio Emilia, Modena, Italy.
Gerunda
Giorgio E
GE
University of Modena and Reggio Emilia, Modena, Italy.
Torelli
Giuseppe
G
University of Modena and Reggio Emilia, Modena, Italy.
Esposito
Roberto
R
University of Modena and Reggio Emilia, Modena, Italy.
Fabbri
Leonardo M
LM
University of Modena and Reggio Emilia, Modena, Italy.