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

Abstract

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.

Effectiveness of interventions for diagnosis and treatment of tuberculosis in hard-to-reach populations in countries of low and medium tuberculosis incidence: a systematic review

“…63 TB screening by IGRA / TST -Neither QFT-G nor TST are good screening tools for TB screening in migrants from high incidence countries with a high BCG vaccination coverage. 31 -There is no difference in sensitivity between QFT-G and TST-10 for culture confirmed TB cases in migrants from high incidence countries with high BCG vaccination coverage. However, QFT-G had a higher sensitivity than TST-15 (86•4% versus 52•3%, p<0•001).…”

“…Characteristics for all nineteen included studies are described in Table 1, evidence tables are in Supplementary Material IV. Twelve of the included studies focussed on migrants, [29][30][31][32][33][34][35][36]38,41,43,45 of which one focussed on children. 41 Three studies focussed on mixed hard-to-reach populations; 39, 42,46 two on drug users; 40,44 one on people living with HIV 47 and one on homeless people.…”

“…Eight studies were conducted in the EU, two in the United Kingdom (UK), 39,42 one in Estonia, 44 one in France, 37 one in Germany, 46 one in Italy, 47 one in Norway 32 and one in Portugal. 40 The remaining eleven studies were conducted outside the EU, eight in the United States (US), 29,31,[33][34][35][36]41,43 two in Israel 30,38 and one in Switzerland. 45 The interventions to improve identification of TB applied active case finding by using (mobile) CXR, 30,[37][38][39]42 symptom-based questionnaire, 45 TST or IGRA 31,36,41 ; adding sputum smear 34,39 or sputum culture 29,33,43 to a screening algorithm; and active referral to a TB clinic.…”

“…Post-migration screening by symptom-based questionnaire does not seem to be effective, 45 and incarceration negatively affects treatment completion in mixed hard-to-reach populations (80% drug users). 74 No clear conclusions can be drawn about the effectiveness of QFT-G and TST for the identification of active TB in migrants 31,36 and children adopted from high-incidence areas. 41…”

“…This systematic review identified 19 new studies [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] published between 2010 and 2015, on top of the 26 studies, published between 1990 and 2010, identified for the NICE reviews. 24,25…”