Overseas culture-based tuberculosis screening in U.S.-bound immigrants and refugees substantially reduced the importation of multidrug-resistant TB into the U.S., researchers reported.
“Approximately two-thirds of new cases of TB and 85% of new cases of [multidrug-resistant TB] in the United States are among non-U.S.-born persons,” Yecai Liu, from thedivision of global migration and quarantine at the CDC, told Healio. “Yet, the epidemiology of [multidrug-resistant TB] in US-bound immigrants and refugees has not been thoroughly studied by using national datasets.”
The study, published in Annals of the American Thoracic Society, utilized data from immigrants and refugees who completed culture-based overseas TB screening from 2015 to 2019. The researchers identified 3,300 culture-positive TB cases. Liu and colleagues compared mean annual number of multidrug-resistant TB cases in non-U.S.-born persons within 1 year of arrival in the U.S. from 1996 to 2006 when overseas TB screening followed a smear-based algorithm and 2014 to 2019 when the overseas TB screening using a culture-based algorithm was fully implemented.
Of all positive TB cases from overseas culture-based screening, 84.1% had rifampicin- and isoniazid-susceptible TB, 11.6% had isoniazid-resistant TB, 3.7% had multidrug-resistant TB and 0.6% had rifampicin-resistant TB.
No individuals had extensively drug-resistant TB, according to the researchers.
Culture-based overseas TB screening among these individuals prevented 24.4 multidrug-resistant TB cases per year in the U.S., which was 18.2 cases more than smear-based overseas TB screening.
In addition, the mean annual number of multidrug-resistant TB cases among non-U.S.-born persons within 1 year of U.S. arrival decreased from 34.6 cases in 1996-2006 to 19.5 cases in 2014-2019 (P < .001).
“Previous studies show that culture-based overseas TB screening in U.S.-bound immigrants and refugees substantially reduces the importation of TB into the U.S., but it was unclear to what extent this intervention prevents the importation of multidrug-resistant TB. This analysis shows that culture-based overseas TB screening is also effective in finding and treating U.S.-bound immigrants and refugees with multidrug-resistant TB before their arrival to the U.S. Identifying and treating multidrug-resistant TB overseas improves the health of immigrants and refugees resettling to the United States and helps to maintain a low burden of multidrug-resistant TB in the U.S.,” Liu told Healio.
The researchers said there is still more to learn about the effectiveness of culture-based overseas TB screening as studied.
“Non-US-born persons are not limited to immigrants and refugees,” Liu said. “For example, we still do not have information on how well a similar program would work in finding and treating cases in U.S.-bound students/exchange visitors or temporary workers from countries with a high incidence of TB.”