title: Interferon gamma release assays for the diagnosis of latent TB infection in HIV-infected individuals in a low TB burden country.
abstract: BACKGROUND
  Interferon gamma release assays (IGRAs) are used to diagnose latent tuberculosis infection. Two IGRAs are commercially available: the Quantiferon TB Gold In Tube (QFT-IT) and the T-SPOT.TB. There is debate as to which test to use in HIV+ individuals. Previous publications from high TB burden countries have raised concerns that the sensitivity of the QFT-IT assay, but not the T-SPOT.TB, may be impaired in HIV+ individuals with low CD4+ T-cell counts. We sought to compare the tests in a low TB burden setting.
  
  
  RESULTS
  T-SPOT.TB, QFT-IT, and tuberculin skin tests (TST) were performed in HIV infected individuals. Results were related to patient characteristics. McNemar's test, multivariate regression and correlation analysis were carried out using SPSS (SPSS Inc). 256 HIV infected patients were enrolled in the study. The median CD4+ T-cell count was 338 cells/µL (range 1-1328). 37 (14%) patients had a CD4+ T-cell count of <100 cells/µL. 46/256 (18% ) of QFT-IT results and 28/256 (11%) of T-SPOT.TB results were positive. 6 (2%) of QFT-IT and 18 (7%) of T-SPOT.TB results were indeterminate. An additional 9 (4%) of T-SPOT.TB results were unavailable as tests were not performed due to insufficient cells or clotting of the sample. We found a statistically significant association between lower CD4+ T-cell count and negative QFT-IT results (OR 1.055, p=0.03), and indeterminate/unavailable T-SPOT.TB results (OR 1.079, p=0.02).
  
  
  CONCLUSIONS
  In low TB prevalence settings, the QFT-IT yields more positive and fewer indeterminate results than T-SPOT.TB. Negative results on the QFT-IT and indeterminate/unavailable results on the T-SPOT.TB were more common in individuals with low CD4+ T-cell counts.
authors: Department of Genito-Urinary Medicine and Infectious Diseases, St James's Hospital, Dublin, Ireland. nicheacm@tcd.ie
authors: Clíona Ní
authors: CN
authors: Cheallaigh
authors: Ian
authors: I
authors: Fitzgerald
authors: Jacinta
authors: J
authors: Grace
authors: Gurmit Jagjit
authors: GJ
authors: Singh
authors: Nahla
authors: N
authors: El-Eraki
authors: Noel
authors: N
authors: Gibbons
authors: Joseph
authors: J
authors: Keane
authors: Thomas R
authors: TR
authors: Rogers
authors: Susan
authors: S
authors: Clarke
authors: Colm
authors: C
authors: Bergin
mesh_terms: D000328:Adult; D000368:Aged; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D005260:Female; D006678:HIV / Q000472:pathogenicity; D015658:HIV Infections / Q000150:complications / Q000473:pathology* / Q000821:virology; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism*; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D014374:Tuberculin Test
chemical_list: D007371:Interferon-gamma
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