Tuberculosis screening of immigrants to low-prevalence countries. A cost-effectiveness analysis.

Abstract

All adult immigrant applicants to Canada undergo chest radiographic screening for tuberculosis (TB). Tuberculin skin testing could reduce the number of chest X-rays, and identify more candidates for prophylaxis. We modeled the cost-effectiveness of chest radiography and tuberculin skin testing for TB prevention over a 20-yr time frame, among three simulated cohorts of 20-yr-old immigrants. Compared with no screening, radiographic screening prevented 4.3% of expected active TB cases in the highest risk cohort (50% TB-infected, 10% human immunodeficiency virus [HIV] seroprevalence), and 8.0% in the lowest risk cohort (5% TB-infected, 1% HIV seroprevalence). Tuberculin skin testing further reduced the expected incidence 8.0% and 4.0%, respectively. Compared with no screening, radiographic screening cost $3,943 Canadian per active TB case prevented in the highest risk cohort, and $236,496 per case prevented in the lowest risk group. Compared with radiographic screening, mass tuberculin skin testing cost $32,601 per additional case prevented in the highest risk group, and $68,799 per additional case prevented in the lowest risk group. Chest radiographic screening of young immigrants from countries with a high prevalence of TB is a relatively inexpensive means of TB prevention. Tuberculin skin testing is considerably less cost-effective. For immigrants from low-prevalence countries, both interventions are extremely costly with negligible impact. The cost-effectiveness of either strategy would be greatly enhanced by increased adherence to chemoprophylaxis recommendations. Radiographic screening of groups with a high prevalence of tuberculous infection will then likely save money.