title: Poor agreement between interferon-gamma release assays and the tuberculin skin test among HIV-infected individuals in the country of Georgia.
abstract: BACKGROUND
  Improved tests to diagnose latent TB infection (LTBI) are needed. We sought to evaluate the performance of two commercially available interferon-gamma release assays (IGRAs) compared to the tuberculin skin test (TST) for the diagnosis of LTBI and to identify risk factors for LTBI among HIV-infected individuals in Georgia, a country with high rates of TB.
  
  
  METHODS
  HIV-patients were enrolled from the National AIDS Center in Tbilisi, Georgia. After providing informed consent, each participant completed a questionnaire, had blood drawn for QuantiFERON-TB Gold in-Tube (QFT-GIT) and T-SPOT.TB testing and had a TST placed. The TST was read at 48-72 hrs with ≥ 5 mm induration considered positive.
  
  
  RESULTS
  Between 2009-2011, 240 HIV-infected persons (66% male) with a median age of 38 years and a median CD4 count of 255 cells/μl (IQR: 124-412) had diagnostic testing for LTBI performed. 94% had visible evidence of a BCG scar. The TST was positive in 41 (17%) patients; QFT-GIT in 70 (29%); and T-SPOT.TB in 56 (24%). At least one diagnostic test was positive in 109 (45%) patients and only among 13 (5%) patients were all three tests positive. Three (1%) QFT-GIT and 19 (8%) T-SPOT.TB test results were indeterminate. The agreement among all pairs of tests was poor: QFT-GIT vs. T-SPOT.TB (κ = 0.18, 95% CI .07-.30), QFT-GIT vs. TST (κ = 0.29, 95% CI .16-.42), and TST vs. T-SPOT.TB (κ = 0.22, 95% CI .07-.29). Risk factors for LTBI varied by diagnostic test and none showed associations between positive test results and well-known risk factors for TB, such as imprisonment, drug abuse and immunological status.
  
  
  CONCLUSIONS
  A high proportion of HIV patients had at least one positive diagnostic test for LTBI; however, there was very poor agreement among all tests. This lack of agreement makes it difficult to know which test is superior and most appropriate for LTBI testing among HIV-infected patients. While further follow-up studies will help determine the predictive ability of different LTBI tests, improved modalities are needed for accurate detection of LTBI and assessment of risk of developing active TB among HIV-infected patients.
authors.affiliation: Infectious Diseases, AIDS and Clinical Immunology Research Center, 16 Al, Kazbegi Avenue, Tbilisi, 0160, Georgia. nikoloch@yahoo.com.
authors.forename: Nikoloz
authors.initials: N
authors.lastname: Chkhartishvili
authors.forename: Russell R
authors.initials: RR
authors.lastname: Kempker
authors.forename: Natia
authors.initials: N
authors.lastname: Dvali
authors.forename: Lela
authors.initials: L
authors.lastname: Abashidze
authors.forename: Lali
authors.initials: L
authors.lastname: Sharavdze
authors.forename: Pati
authors.initials: P
authors.lastname: Gabunia
authors.forename: Henry M
authors.initials: HM
authors.lastname: Blumberg
authors.forename: Carlos
authors.initials: C
authors.lastname: Del Rio
authors.forename: Tengiz
authors.initials: T
authors.lastname: Tsertsvadze
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count; D005260:Female; D005846:Georgia (Republic); D015658:HIV Infections / Q000382:microbiology*; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods* / Q000592:standards*; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000821:virology*; D008297:Male; D015203:Reproducibility of Results; D012307:Risk Factors; D014374:Tuberculin Test / Q000379:methods* / Q000592:standards*