Tuberculin Skin Tests versus Interferon-Gamma Release Assays in Tuberculosis Screening among Immigrant Visa Applicants

Tuberculosis research and treatment 03/2014; 2014:217969. DOI: 10.1155/2014/217969
Source: PubMed


Objective. Use of tuberculin skin tests (TSTs) and interferon gamma release assays (IGRAs) as part of tuberculosis (TB) screening among immigrants from high TB-burden countries has not been fully evaluated. Methods. Prevalence of Mycobacterium tuberculosis infection (MTBI) based on TST, or the QuantiFERON-TB Gold test (QFT-G), was determined among immigrant applicants in Vietnam bound for the United States (US); factors associated with test results and discordance were assessed; predictive values of TST and QFT-G for identifying chest radiographs (CXRs) consistent with TB were calculated. Results. Of 1,246 immigrant visa applicants studied, 57.9% were TST positive, 28.3% were QFT-G positive, and test agreement was 59.4%. Increasing age was associated with positive TST results, positive QFT-G results, TST-positive but QFT-G-negative discordance, and abnormal CXRs consistent with TB. Positive predictive values of TST and QFT-G for an abnormal CXR were 25.9% and 25.6%, respectively. Conclusion. The estimated prevalence of MTBI among US-bound visa applicants in Vietnam based on TST was twice that based on QFT-G, and 14 times higher than a TST-based estimate of MTBI prevalence reported for the general US population in 2000. QFT-G was not better than TST at predicting abnormal CXRs consistent with TB.

Download full-text


Available from: William C. Whitworth, Mar 09, 2014
24 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The goal of this study was to evaluate the effect of the specimen-processing method that uses the detergent C18-carboxypropylbetaine (CB-18) on the sensitivity of acid-fast bacillus (AFB) staining. Vietnamese immigrants with abnormal chest radiographs provided up to three sputum specimens, which were examined for acid-fast bacilli by use of direct auramine and Ziehl-Neelsen staining. The remaining sputum was split; half was cultured, and the other half was incubated with CB-18 for 24 h, centrifuged, and examined for AFB by both staining methods. CB-18 processing improved the sensitivity of AFB staining by 20 to 30% (only differences in auramine sensitivity were statistically significant) but reduced specificity by approximately 20% (P < 0.05). These findings have direct utility for overseas migrant tuberculosis screening programs, for which maximizing test sensitivity is a major objective.
    Journal of Clinical Microbiology 07/2005; 43(7):3460-2. DOI:10.1128/JCM.43.7.3460-3462.2005 · 3.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tuberculosis cases in foreign-born persons account for more than 50% of all tuberculosis cases in the United States. The Institute of Medicine has recommended enhancing overseas screening as one measure to support tuberculosis elimination efforts. We assessed the ability of overseas tuberculosis screening (chest radiograph followed by 3 acid-fast bacilli sputum smears for persons with abnormal chest radiographs [suggestive of active tuberculosis]) to detect pulmonary tuberculosis disease among US-bound immigrants with abnormal chest radiographs. During October 1998 to October 1999, 14 098 US immigrant visa applicants were screened overseas in Vietnam. Adult applicants with abnormal chest radiographs were enrolled to assess screening test characteristics among this group using mycobacterial culture as the gold standard for pulmonary tuberculosis disease diagnosis. Risk factors for pulmonary tuberculosis disease were also evaluated. Among 1179 adult applicants with abnormal chest radiographs, 82 (7.0%) had positive acid-fast bacilli smear results, and 183 (15.5%) had positive Mycobacterium tuberculosis culture results (pulmonary tuberculosis disease). The sensitivity, specificity, and positive and negative predictive values of serial acid-fast bacilli screening among this group were 34.4% (63/183), 98.1% (977/996), 76.8% (63/82), and 89.1% (977/1097), respectively. Risk factors for pulmonary tuberculosis disease included younger age (18-34 years), no history of tuberculosis or treatment, reported symptoms, and cavitation or consolidation on chest radiograph. The ability of current overseas screening to detect tuberculosis among immigrants with abnormal chest radiographs is low. Improved diagnostic methods, enhanced screening measures, and postmigration follow-up are essential to control tuberculosis among immigrants and support US and global tuberculosis elimination.
    Archives of Internal Medicine 02/2006; 166(2):234-40. DOI:10.1001/archinte.166.2.234 · 17.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A recently developed whole-blood interferon gamma (IFN-gamma) assay based on stimulation with the Mycobacterium tuberculosis-specific antigens early secreted antigenic target 6 and culture filtrate protein 10 shows promise for the diagnosis of latent tuberculosis (TB) infection. To compare the tuberculin skin test (TST) and the whole-blood IFN-gamma assay in the diagnosis of latent TB infection according to the intensity of exposure. A prospective comparison between the whole-blood IFN-gamma assay and the TST using a 2-TU dose of purified protein derivative RT23 in a population with intermediate TB burden was conducted sequentially between February 1, 2004, and February 28, 2005, in a Korean tertiary referral hospital. Of 273 participants, 220 (95.7%) had received BCG vaccine. Participants were grouped according to their risk of infection: group 1, no identifiable risk of M tuberculosis infection (n = 99); group 2, recent casual contacts (n = 72); group 3, recent close contacts (n = 48); group 4, bacteriologically or pathologically confirmed TB patients (n = 54). Levels of agreement between the TST and the IFN-gamma assay and the likelihood of infection in the various groups. For the TST with a 10-mm induration cutoff, the positive response rate in group 1 was 51%; group 2, 60%; group 3, 71%, and group 4, 78%. For the IFN-gamma assay, the positive response rate in group 1 was 4%; group 2, 10%; group 3, 44%; and group 4, 81%. The overall agreement between the TST and the IFN-gamma assay in healthy volunteers was kappa = 0.16. The odds of a positive test result per unit increase in exposure across the 4 groups increased by a factor of 5.31 (95% confidence interval [CI], 3.62-7.79) for the IFN-gamma assay and by a factor of 1.52 (95% CI, 1.20-1.91) for the TST (P<.001). Using a 15-mm induration cutoff for the TST did not make a substantial difference to the test results. The IFN-gamma assay is a better indicator of the risk of M tuberculosis infection than TST in a BCG-vaccinated population.
    JAMA The Journal of the American Medical Association 07/2005; 293(22):2756-61. DOI:10.1001/jama.293.22.2756 · 35.29 Impact Factor
Show more