Decrease in foreign-born tuberculosis linked to culture-based screening

1. From a cross-sectional study, the implementation of a new culture-based tuberculosis (TB) screening algorithm for immigrants was associated with a reduction in the annual number of TB cases.

2. The number of smear-negative/culture-positive TB cases successfully diagnosed abroad increased from 4 to 629 during the same period.

Evidence Rating Level: 2 (Good)

Study Rundown: Immigrants account for the majority of new tuberculosis (TB) cases diagnosed annually in the United States. To combat this, U.S. immigrants must pass a TB screening protocol, which before 2007 included a chest X-ray and a smear-based algorithm. However, because cases of TB remained undetected, the CDC added a culture-based screening algorithm. This study examined the effect of the culture-based algorithm on new TB diagnoses in the U.S. and abroad from 2007 to 2012. Before implementation of the culture-based algorithm, the average number of new TB cases diagnosed annually in the U.S. was 1504. During implementation, the number of new cases dropped to 940 in 2012, while the number of smear-negative/culture-positive cases diagnosed abroad increased during the same time period. The total number of smear-negative/culture-positive cases diagnosed from 2007 to 2012 was 2195. The study is limited in that it did not control for the decline in the amount of non-immigrant visitors to U.S. and the decline in TB incidence in their countries of origin. Overall, the new protocol was associated with the import of fewer cases of TB into the U.S.

Click to read the study, published today in the Annals of Internal Medicine

Relevant Reading: Overseas screening for tuberculosis in U.S.-bound immigrants and refugees

In-Depth [cross-sectional study]: The study examined TB screening records of 3 212 421 immigrants and refugees who arrived in the U.S. between 2007 and 2012. Of this population, 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 people screened by the culture-based algorithm, 4032 were diagnosed with TB, and 2195 of these cases were smear-negative/culture-positive. The number of U.S. immigrant TB cases dropped from 1511 in 2007 to 940 in 2012, which coincided with a 157-fold increase in smear-negative/culture-positive TB diagnoses made overseas during the same period (4 in 2007 vs. 629 in 2012).

Image: PD

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