Poor agreement between interferon-gamma release assays and the tuberculin skin test among HIV-infected individuals in the country of Georgia

• Type of Material: Article
• Authors: Nikoloz Chkhartishvili, AIDS and Clinical Immunology Research Center; Russell Ryan Kempker, Emory University; Natia Dvali, AIDS and Clinical Immunology Research Center; Lela Abashidze, AIDS and Clinical Immunology Research Center; Lali Sharavdze, AIDS and Clinical Immunology Research Center; Pati Gabunia, AIDS and Clinical Immunology Research Center; Henry Michael Blumberg, Emory University; Carlos Del Rio, Emory University; Tengiz Tsertsvadze, AIDS and Clinical Immunology Research Center
• Language: English
• Date: 2013
• Publisher: BioMed Central
• Publication Version: Final Published Version
• Copyright Statement: © 2013 Chkhartishvili et al.; licensee BioMed Central Ltd.
• License: Creative Commons Attribution 2.0 Generic
• Final Published Version (URL): http://www.biomedcentral.com/1471-2334/13/513
• Title of Journal or Parent Work: BMC Infectious Diseases
• ISSN: 1471-2334
• Volume: 13
• Issue: 513
• Grant/Funding Information: This study was supported in part by the U.S. Civilian Research and Development Foundation (CRDF) award #GEB1-2939-TB-08; the NIH/FIC through the Emory AIDS International Training and Research Program award #D43 TW01042 and the Emory-Georgia Tuberculosis Research Training Program award # D43TW007124; the NIH/NIAID Emory Center for AIDS Research award #;P30 AI 50409 and NIH NIAID K23 AI103044-01.
• Keywords: Latent tuberculosis infection; TST; Eastern Europe; Screening; Interferon-gamma
• Research Categories: Health Sciences, Public Health; Health Sciences, Immunology; Health Sciences, General

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.