A culture-based screening algorithm may significantly reduce the incidence of tuberculosis among immigrants and refugees bound for the United States, according to CDC researchers.
“Before 2007, the mandated overseas TB screening was based on a smear-based algorithm that could not diagnose smear-negative/culture-positive TB,” the researchers wrote in Annals of Internal Medicine. “By increasing the number of cases diagnosed and treated overseas among immigrants and refugees bound for the United States, the implementation of the culture-based algorithm [in 2007] contributed to the decline of foreign-born TB incidence in the United States.”
The CDC revised the smear-based TB screening algorithm in 2007 to detect cases that were smear-negative, but culture-positive. The researchers evaluated its effect in a population-based cross-sectional study that included 3,212,421 immigrants and refugees entering the U.S. from 2007 to 2012. Approximately half were screened with the smear-based algorithm, and the other half were screened with the culture-based algorithm.
Data about cases diagnosed by the smear-based TB algorithm were not reported to the CDC. Among the 1,561,460 people screened by the culture-based algorithm, there were 4,032 cases of TB, a rate of 258 cases per 100,000 persons. Among those, 54.4% had smear-negative/culture-positive TB.
Before culture-based screening was implemented, there was an annual mean of 1,504 cases of TB among foreign-born individuals within 1 year after arrival to the U.S. While the culture-based screening was being implemented, the annual number of cases dropped to 940. In addition, the annual number of smear-negative/culture-positive TB cased diagnosed overseas increased from four to 629 during the same period.
“Culture-based overseas TB screening is a high-yield intervention for preventing TB in immigrants and refugees bound for the United States,” the researchers wrote. “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.” – by Emily Shafer
Disclosure: The researchers report no relevant financial disclosures.