title: IFN-γ response on T-cell based assays in HIV-infected patients for detection of tuberculosis infection.
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.
authors.affiliation: Servei de Microbiologia, Hospital Universitari Germans Trias i Pujol, Fundació Institut en Ciències de Salut Germans Trias i Pujol, Badalona, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Latorre
authors.forename: Xavier
authors.initials: X
authors.lastname: Martínez-Lacasa
authors.forename: Roser
authors.initials: R
authors.lastname: Font
authors.forename: Alicia
authors.initials: A
authors.lastname: Lacoma
authors.forename: Jordi
authors.initials: J
authors.lastname: Puig
authors.forename: Cristina
authors.initials: C
authors.lastname: Tural
authors.forename: Josep
authors.initials: J
authors.lastname: Lite
authors.forename: Cristina
authors.initials: C
authors.lastname: Prat
authors.forename: Eva
authors.initials: E
authors.lastname: Cuchi
authors.forename: Vicente
authors.initials: V
authors.lastname: Ausina
authors.forename: Jose
authors.initials: J
authors.lastname: Domínguez
mesh_terms: D000328:Adult; D001500:BCG Vaccine / Q000008:administration & dosage; D018791:CD4 Lymphocyte Count; D058501:Enzyme-Linked Immunospot Assay; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000276:immunology* / Q000382:microbiology; D006801:Humans; D007371:Interferon-gamma / Q000097:blood* / Q000276:immunology; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D013601:T-Lymphocytes / Q000276:immunology; D014374:Tuberculin Test
chemical_list: D001500:BCG Vaccine; D007371:Interferon-gamma