More vigilence needed for foreign-born screening

Screening high-risk immigrants and their close contacts for tuberculosis can improve the diagnosis and treatment of TB in people born outside the United States at a time when TB among the foreign-born is increasing, according to a new study published by the American Lung Association.

TB cases in the United States declined 7% in 1996, the fourth consecutive year in which total cases have declined. Yet, TB cases among U.S. residents born outside the United States continue to increase as a proportion of total cases, rising from 22% of U.S. cases in 1986 to 37% in 1996.

The new study, conducted by researchers at the Centers for Disease Control and Prevention and the Seattle-King County (WA) Department of Public Health, examined the effectiveness of several strategies to help combat this rising problem. Researchers analyzed a Seattle program which provided additional screening and treatment upon arrival in the United States for people found to have abnormal chest X-rays during immigration screening.

The study appears in the August issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Lung Association in New York City.

Latent infection may go undetected

Individuals applying for immigration are currently having chest X-rays taken in their home country and are being provided with treatment if they are diagnosed with active TB disease. But according to study researchers, many people who do not have active disease during this screening process may have latent TB infection and will go on to develop disease after arriving in the United States.

"Our study clearly demonstrates that targeted screening of high-risk immigrants and their families and close contacts can be an effective strategy for TB prevention in this country," said co-author Nancy Binkin, MD, MPH, an epidemiologist at the CDC’s Division of TB Elimination.

The study found that between 1992 and 1994, 74% of high-risk immigrants tested positive for TB infection. Five percent had active TB disease and were immediately started on treatment to combat the disease, and an additional 34% were provided preventive therapy to stop the latent TB germ from developing into active disease.

Public health officials were able to identify additional individuals in need of preventive therapy through screening of families and close contacts of TB patients. Researchers found that 40% of close contacts screened needed preventive therapy.

By contrast, 23% of the contacts of U.S. born individuals with active TB required preventive therapy. Researchers believe the higher risk results from both the increased likelihood of exposure in countries where TB is prevalent and the fact that these individuals typically have more family members living in the same household than U.S.-born families.