Tuberculosis Screening by Tuberculosis Skin Test or QuantiFERON®-TB Gold In-Tube Assay among an Immigrant Population with a High Prevalence of Tuberculosis and BCG Vaccination

Abstract

RationaleEach year 1 million persons acquire permanent U.S. residency visas after tuberculosis (TB) screening. Most applicants undergo a 2-stage screening with tuberculin skin test (TST) followed by CXR only if TST-positive at > 5 mm. Due to cross reaction with bacillus Calmette-Guérin (BCG), TST may yield false positive results in BCG-vaccinated persons. Interferon gamma release assays exclude antigens found in BCG. In Vietnam, like most high TB-prevalence countries, there is universal BCG vaccination at birth. Objectives1. Compare the sensitivity of QuantiFERON ®-TB Gold In-Tube Assay (QFT) and TST for culture-positive pulmonary TB. 2. Compare the age-specific and overall prevalence of positive TST and QFT among applicants with normal and abnormal CXR.MethodsWe obtained TST and QFT results on 996 applicants with abnormal CXR, of whom 132 had TB, and 479 with normal CXR. ResultsThe sensitivity for tuberculosis was 86.4% for QFT; 89.4%, 81.1%, and 52.3% for TST at 5, 10, and 15 mm. The estimated prevalence of positive results at age 15–19 years was 22% and 42% for QFT and TST at 10 mm, respectively. The prevalence increased thereafter by 0.7% year of age for TST and 2.1% for QFT, the latter being more consistent with the increase in TB among applicants.ConclusionsDuring 2-stage screening, QFT is as sensitive as TST in detecting TB with fewer requiring CXR and being diagnosed with LTBI. These data support the use of QFT over TST in this population.

Decline in Tuberculosis among Mexico-Born Persons in the United States, 2000–2010

“…A recent study concluded that elevated tuberculosis case rates among newly arrived persons might be primarily due to prevalent tuberculosis rather than a higher risk of reactivation (18). This finding further supports the focus of targeted testing on newly arrived Mexico-born persons, (most of whom have not passed through preimmigration screening), as targeted testing might also detect prevalent tuberculosis disease (36). …”

“…Strategies such as targeted testing for latent tuberculosis infection among subgroups of non–recently arrived Mexico-born persons with higher risk for progression to tuberculosis disease (e.g., diabetes mellitus) might be more feasible and cost effective (10, 12, 39, 40). In addition, new tools against latent tuberculosis infection, including more specific diagnostics (36, 41) and shorter courses of therapy (42), could help alleviate the workload of treatment for this population.…”

A Systematic Review on TST and IGRA Tests Used for Diagnosis of LTBI in Immigrants

“…Across the 51 studies, 34 studies looked at TST alone and 9 studies looked at IGRAs alone [57][58][59][60][61][62][63][64][65]; 8 studies compared TST and IGRAs [66][67][68][69][70][71][72][73]. Just 8 studies excluded those with active TB from their study [23,32,34,50,66,68,69,71].…”

“…Just 8 studies excluded those with active TB from their study [23,32,34,50,66,68,69,71]. Only 16 studies reported on BCG vaccination with 9 using BCG scar as evidence of vaccination [28,32,33,53,55,58,60,71,72], 5 using BCG self-reporting as evidence [23,29,35,66,69], and 2 using BCG vaccination schedule in country of origin as a proxy for BCG vaccination [48,73], although BCG vaccination rates varied considerably across studies (0-100 %). The characteristics of the 51 included studies are included in Table 1 and in the supplementary text, which summarizes each of the 51 studies included in the review.…”

Is Tuberculosis Still a Threat in the Developed World? Two Cases of Tuberculosis Masquerading as Gynecologic Cancers

“…An inexpensive tuberculin purified protein derivative (PPD) skin test can quickly screen for both active and latent TB infections. Interferon-based blood tests like QuantiFERON ® -TB Gold are preferred over PPDs for patients with a history of Bacille Calmette-Guerin vaccination, a vaccine commonly administered in developing countries [39,40]. These tests are informative in suggesting a history of TB exposure, but they do not rule out the possibility of a coexisting gynecologic cancer.…”