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Open Access Research article

IFN-γ response on T-cell based assays in HIV-infected patients for detection of tuberculosis infection

Irene Latorre145, Xavier Martínez-Lacasa6, Roser Font6, Alicia Lacoma145, Jordi Puig234, Cristina Tural234, Josep Lite7, Cristina Prat145, Eva Cuchi7, Vicente Ausina145 and Jose Domínguez145*

Author Affiliations

1 Servei de Microbiologia. Hospital Universitari Germans Trias i Pujol. Fundació Institut en Ciències de la Salut Germans Trias i Pujol. Badalona. Spain

2 Servei de Medicina Interna. Hospital Universitari Germans Trias i Pujol. Fundació Institut en Ciències de la Salut Germans Trias i Pujol. Badalona. Spain

3 Unidad Clínica HIV. Hospital Universitari Germans Trias i Pujol. Fundació Institut en Ciències de la Salut Germans Trias i Pujol. Badalona. Spain

4 Universitat Autònoma de Barcelona. Bellaterra. Spain

5 Ciber Enfermedades Respiratorias. Instituto de Salud Carlos III. Badalona. Spain

6 Unidad Control de la Tuberculosis/HIV. Hospital Universitari Mútua Terrassa. Spain

7 Catlab. Terrassa. Spain

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BMC Infectious Diseases 2010, 10:348  doi:10.1186/1471-2334-10-348

Published: 10 December 2010

Abstract

Background

Individuals infected with human immunodeficiency virus (HIV) have an increased risk of progression to active tuberculosis following Mycobacterium tuberculosis infection. The objective of the study was to determine IFN-γ responses for the detection of latent tuberculosis infection (LTBI) with QuantiFERON-TB GOLD In Tube (QFT-G-IT) and T-SPOT.TB in HIV patients, and evaluate the influence of CD4 cell count on tests performance.

Methods

We studied 75 HIV patients enrolled for ongoing studies of LTBI with T-SPOT.TB, QFN-G-IT and TST. Mean CD4 cell counts ± standard deviation was 461.29 ± 307.49 cells/μl. Eight patients had a BCG scar.

Results

T-SPOT.TB, QFN-G-IT and TST were positive in 7 (9.3%), 5 (6.7%) and 9 (12%) cases, respectively. Global agreement between QFN-G-IT and T-SPOT.TB was 89% (κ = 0.275). The overall agreement of T-SPOT.TB and QFN-G-IT with TST was 80.8% (κ = 0.019) and 89% (κ = 0.373), respectively. We have found negative IFN-γ assays results among 2 BCG-vaccinated HIV-infected individuals with a positive TST. In non BCG-vaccinated patients, QFN-G-IT and TST were positive in 5 cases (7.5%) and T-SPOT.TB in 7 (10.4%). In contrast, in BCG-vaccinated patients, only TST was positive in 4/8 (50%) of the cases. The differences obtained in the number of positive results between TST and both IFN-γ assays in BCG vaccinated patients were significant (95% CI 3-97%, p = 0.046), however, the confidence interval is very wide given the small number of patients. In patients with CD4< 200, we obtained only one (5%) positive result with T-SPOT.TB; however, QFN-G-IT and TST were negative in all cases. On the contrary, percentages of positive results in patients with CD4> 200 were 10.9% (6/55), 9.1% (5/55) and 16.4% (9/55) with T-SPOT.TB, QFN-G-IT and TST, respectively.

Conclusions

IFN-γ tests have the benefit over TST that are less influenced by BCG vaccination, consequently they are more specific than TST. Although our number of patients with advance immunosuppression is limited, our study suggests that IFN-γ assays are influenced with level of immunosuppression. The use of IFN-γ assays could be a helpful method for diagnosing LTBI in HIV population.