When finding and treating latent tuberculosis in the United States, higher yields are found in foreign-born persons who have recently entered the country from certain high-risk populations, including individuals from sub-Saharan Africa and Southeast Asia, according to a study released on July 22 in JAMA.
Tuberculosis (TB) control has improved progressively over the last years. “From 1993 to 2006, the number of tuberculosis (TB) cases in the United States decreased by 45 percent, from 25,107 to 13,779. This decline has occurred disproportionately among the U.S.-born population, for whom the number of cases has declined by 66 percent, while the number of TB cases among foreign-born persons in the United States increased by 5 percent,” write the authors. They continue, expanding the statistics: “In 2006, 57 percent of all reported TB cases were among foreign-born persons.” They continue, stating that the current TB control strategies are not sufficiently addressing the population when targeting TB disease and latent TB infection (LTBI).
To expand upon this, Kevin P. Cain, M.D., of the Centers for Disease Control and Prevention, Atlanta, and colleagues examined observational data collected between 2001 and 2006 related to foreign-born persons in the U.S. to examine which populations are at higher risk for both TB and drug-resistant TB. Over time, in the foreign born population as a whole, the rate of TB cases decreased after entry, but still remained higher than among U.S. born persons, even up to 20 years after arrival. In 2006, a rate of over 100 TB cases per 100,000 recent entrants was reported, a rate more than four times that of the native born population.
Entrants from specific countries showed various trends. For instance, when examining antibiotic resistance among the culture positive entrants, isoniazid resistance was found in 20% of Vietnamese entrants, 18% of Peruvian entrants, 17% of those from the Philippines, and 16% from China. In examining the number of TB cases, annual case rates in individuals born in many of the countries of sub-Saharan Africa were greater than 250 per 100,000 persons during the first two years of entry. At the same time, persons from Central America, Eastern Europe, the Pacific Islands, and South, East, and Central Asia had annual case rates greater than 100 per 100,000 persons in the same amount of time. An average of 250 individuals were diagnosed with smear-negative, culture-positive TB disease within 3 months of entry each year. Of these, 46% were from the Philippines or Vietnam.
The authors point out the need for directed screening efforts for the control of TB in the United States. “With more than 37 million foreign-born persons currently living in the United States, it is not possible to find and test all foreign-born persons for LTBI. This study assists in targeting LTBI screening efforts by examining risk of TB disease among subgroups of foreign-born populations. Finding and treating LTBI among some specific groups of foreign-born persons living in the United States is likely to provide high yield relative to some other TB control strategies. Given current immigration patterns, the impact of culture-enhanced overseas screening of immigrants and refugees is likely be greatest in the Philippines and Vietnam, but may have limited yield for most other countries of birth,” write the authors.
They further recommend that reforms should be made to current TB control measures: “Current strategies for TB control, as presently implemented, are not adequate for achieving TB elimination in the near future. TB control and elimination among foreign-born persons in the United States will require a multifaceted approach. In the future, preventing TB disease among legal immigrants to the United States might best be accomplished through overseas diagnosis and treatment of LTBI prior to immigration. The present use of a 9-month regimen for LTBI treatment makes this strategy impractical. This strategy may be both feasible and high yield when shorter, effective treatment regimens for LTBI become available. Increased investment in global TB control could also result in decreases in U.S. TB rates.”
Tuberculosis Among Foreign-Born Persons in the United States
Kevin P. Cain; Stephen R. Benoit; Carla A. Winston; William R. Mac Kenzie
JAMA. 2008;300(4):405-412.
Written by Anna Sophia McKenney