While the incidence of tuberculosis is decreasing in the United States, more cases are being found among immigrants. The incidence of tuberculosis among foreign-born persons is at least four to five times higher than the incidence in persons born in the United States; the risk of latent tuberculosis infection among foreign-born children also is higher. The risk of infection among immigrant children is not uniform but is dependent on country of origin, time since immigration, bacille Calmette-Guérin (BCG) vaccination, and socioeconomic status.
Mandalakas and Starke reviewed recommendations for tuberculosis screening among immigrant children. The U.S. Immigration and Naturalization Service requires immigrants to have the following evaluations: (1) a brief medical history, (2) a chest radiograph for tuberculosis in persons 15 years of age or older, and (3) tuberculin skin testing for those 15 years of age or younger if the person is ill or has a family member with suspected tuberculosis. A chest radiograph is not obtained, and skin testing is not completed for most children. Local health departments and physicians are expected to identify and screen high-risk children.
The usual screening test for tuberculosis is the Mantoux skin test with five tuberculin units of purified protein derivative. Physicians should read the Mantoux test at 48 to 72 hours after application because parents and other lay persons do not have the ability to read the test results accurately. Skin testing in children who have received the BCG vaccine causes some confusion, although a positive skin test should not be attributed to BCG. Post-BCG–induced tuberculin skin reactions are generally smaller than 10 mm; larger reactions are unlikely five years or more after a single injection of BCG during infancy.
Children who have received multiple BCG vaccinations or a single dose after one year of age can experience post-BCG skin test reactions that are increased in size and that persist for a longer time. Recent skin testing in a child vaccinated with BCG also may cause a booster effect, with the second skin test measuring larger than 10 mm and exceeding the initial skin test reaction by at least 6 mm.
Foreign-born children should receive a skin test on arrival in the United States if they are at high risk when the risk assessment is based on epidemiologic profiles. Children at low risk do not need skin testing. A positive skin test in a high-risk child who has received BCG most likely indicates latent tuberculosis infection. Foreign-born children should be retested if subsequent risk events occur, such as travel to a high-risk country or exposure to high-risk persons. Postponement of skin testing should be considered in children who have recently had BCG vaccination or who recently underwent skin testing. Of course, skin testing should not be deferred in children who are at high risk, who may be lost to follow-up, or who have an illness or abnormal chest radiograph findings.
Foreign-born adoptees are generally at high risk for tuberculosis infection and may be malnourished. Tuberculosis skin testing should be performed early and repeated in six months because of the increased possibility of recent infection. Some experts recommend anergy testing. A chest radiograph should be obtained for high-risk children with a skin test reaction of 5 mm or more. Refugee children also should be screened and probably should undergo chest radiography.
The authors conclude that foreign-born children have a higher risk of latent tuberculosis infection than children born in the United States. This finding mandates effective and timely screening procedures including skin testing and chest radiography, if there are any concerns. Isoniazid can be used to treat foreign-born children with latent tuberculosis infection, unless there is a specific link to a known case of isoniazid-resistant tuberculosis.