Screening Strategy Reduces Incidence of Immigration-Related Tuberculosis

Implementation of the culture-based algorithm may have substantially reduced the incidence of tuberculosis (TB) among newly arrived, foreign-born persons in the United States of America.

Immigration has a substantial effect on the incidence of TB, so immigrants and refugees bound for the USA are required to have overseas TB screening. Before 2007, a smear-based algorithm that could not diagnose smear-negative/culture-positive TB was used to screen this population.

Scientists at the Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) revised the screening strategy to use a more inclusive culture-based algorithm. They reviewed health records to determine the increase of smear-negative/culture-positive Mycobacterium tuberculosis or TB cases diagnosed overseas between 2007 and 2012 and compared that figure with the decline of reported TB cases among foreign-born persons within one year after arrival in the USA.

Of the 3,212,421 arrivals of immigrants and refugees from 2007 to 2012, a total of 1,650,961 (51.4%) were screened by the smear-based algorithm and 1,561,460 (48.6%) were screened by the culture-based algorithm. Among the 4,032 TB cases diagnosed by the culture-based algorithm, 2,195 (54.4%) were smear-negative/culture-positive. Before implementation (2002 to 2006), the annual number of reported cases among foreign-born persons within one year after arrival was relatively constant (range, 1,424 to 1,626 cases; mean, 1,504 cases), but decreased from 1,511 to 940 cases during implementation (2007 to 2012). During the same period, the annual number of smear-negative/culture-positive TB cases diagnosed overseas among immigrants and refugees bound for the USA by the culture-based algorithm increased from 4 to 629.

The authors concluded that the increased annual number of TB cases detected in immigrants and refugees closely matched in magnitude a decrease in the number reported TB cases, suggesting that the culture-based algorithm effectively reduced TB incidence. To further reduce the TB incidence in foreign-born populations, consideration should be given to expanding TB screening to students, exchange visitors, and temporary workers from countries with a high incidence of TB, as well as finding novel strategies to address the large numbers of foreign-born persons with latent TB infection The study was published on March 17, 2015, in the journal Annals of Internal Medicine.

Related Links:
[US] Centers for Disease Control and Prevention