Reduced importation of tuberculosis after the implementation of an enhanced pre-immigration screening protocol

Abstract

Importation of infectious tuberculosis (TB) threatens TB control in California and the United States. To assess the effectiveness of an enhanced pre-immigration screening and treatment protocol to prevent the importation of infectious TB. Retrospective analysis of immigrants ≥ 15 years of age with TB suspect classifications who were screened for TB in their countries of origin before (pre-intervention cohort) and after (post-intervention cohort) implementation of enhanced pre-immigration screening. Enhanced pre-immigration screening added sputum cultures to the existing screening system based on sputum smears for persons with abnormal chest radiographs. The pre- and post-intervention cohorts included respectively 2049 and 1430 immigrants. The occurrence of tuberculosis ≤ 6 months after US arrival in this population decreased following the intervention, from 4.2% (86 cases) to 1.5% (22 cases, P < 0.001). Among pre-intervention cohort cases, 14% were sputum acid-fast bacilli (AFB) smear-positive and 81% were sputum culture-positive for TB, compared with 5% sputum AFB smear-positive (P = 0.46) and 68% sputum culture-positive (P = 0.18) among the post-intervention cohort cases. The enhanced pre-immigration screening was associated with a decline in the proportion of immigrants with TB suspect classifications identified with TB within 6 months of arrival in the United States. Continued state and national surveillance is critical to monitor the effectiveness of the revised pre-immigration screening as it is implemented in additional countries.