Predictive Value of the Tuberculin Skin Test among Newly Arriving Immigrants

RATIONALE Screening and treating newly arriving immigrants for latent tuberculosis infection (LTBI) in low-incidence countries could be promising to reduce the tuberculosis incidence among this population. The effectiveness of screening with the tuberculin skin test (TST) is unknown. OBJECTIVES To estimate the risk of progression to tuberculosis within two years after entry, stratified by TST result at entry. METHODS In a case-base design, we determined the prevalence of TST positives (10 mm and 15 mm) among a representative cohort of immunocompetent immigrants (n = 643) aged ≥18 years who arrived between April 2009 and March 2011 in The Netherlands (base cohort). Immigrants who progressed to tuberculosis within two years after arrival in 2005, 2006 or 2007 were extracted from the Netherlands Tuberculosis Register (case source cohort). The prevalence of TST positives from the base cohort was projected on the case source cohort to estimate the risk of progression to active tuberculosis by using bayesian analyses to adjust for the sensitivity of the TST and Poisson regression analyses to take into account the random error of the number of extracted cases. RESULTS The prevalence of TST positives was 42% and 23% for a cut-off value of 10 mm and 15 mm, respectively. The overall risk of progression to tuberculosis if TST positive was 238 per 100,000 population (95% CI 151-343) and 295 per 100,000 population (95% CI 161-473) for a cut-off value of ≥10 mm and ≥15 mm, respectively. The corresponding risk for TST negatives was 19 (95% CI 0-59) and 58 (95% CI 25-103). CONCLUSION The TST has the discriminatory ability to differentiate between individuals at low and high risk of disease.