Tuberculosis: Important Screening in International Adoptions
Posted on May 9, 2011
It is important for parents of international adoptees to understand the tests necessary for the proper evaluation of their children upon arrival in the United States. One of the most misunderstood is screening for tuberculosis exposure.
According to the World Health Organization website, approximately 1.7 million people died in 2009 from tuberculosis. Countries with the most cases (in descending order) are India, China, Indonesia, Nigeria and South Africa. Ethiopia, Russia and Vietnam are 7, 11 and twelve in the list of countries with most cases. Low socio-economic status, living in orphanages or refugee camps and not having easy access to medical care put international adoptees at great risk for being exposed to tuberculosis.
This risk is best illustrated in an article in the New England Journal of Medicine (vol 341, No 20, 1999, pp 1491-1495). A woman in North Dakota developed tuberculosis of the hip. Three years earlier, she and her husband adopted twin boys (age 6 at the time of the adoption) from the Republic of the Marshall Islands. In investigating the source of the tuberculosis, it was discovered that one of the twins had extensive, bilateral, cavitary pulmonary tuberculosis. Upon arrival in the United States, the child was screened for tuberculosis using a Tine test; it was never read by a health professional. In addition to the immediate family, twenty percent of the children who shared the school bus with the twins, tested positive for tuberculosis. The Centers for Disease Control estimates that the rate of tuberculosis among internationally adopted children is 4 to 6 times that among the general population of the United States.
The Tine test was an old test used for the detection of tuberculosis. It consisted of 4 small pins, coated with dried tuberculosis protein that would puncture the skin. If the person has been exposed to tuberculosis, a reaction of > one millimeter would result in 48-72 hours after the puncture. Because it was impossible to determine the amount of tuberculosis protein deposited under the skin with the Tine test, this test is no longer performed.
Currently, the tuberculin skin test (TST) is called a Mantoux test or PPD (purified protein derivative). One tenth of a millimeter of PPD is injected intradermally in the forearm. The test should be read by a health professional in 48-72 hours after placing. The amount of induration (raised hard area) is measured in millimeters.
Many international adoptees have previously received a vaccine against tuberculosis called BCG. This is frequently given in the deltoid muscle and leaves a raised, slightly curved scar on the skin. However, the vaccine is not very effective. In young children, the estimated protective efficacy rates of the vaccine have ranged from 52% to 100% for prevention of tuberculous meningitis and miliary TB and from 2% to 80% for prevention of pulmonary TB. So the listing of a BCG on a foreign vaccine record or the presence of a scar on the deltoid does not mean protection from tuberculosis.
A history of having a BCG can result in confusion in interpreting the TST. After having received a BCG, the TST frequently results in 5 mm of induration, and very rarely greater than 15 mm of induration. The Centers for Disease Control, the American Academy of Pediatrics and the American Thorax Association all accept a maximum of 10 mm as a BCG reaction. Any more most probably indicates exposure to tuberculosis.
There is now a blood test that can help in determining exposure to tuberculosis (QuantiFERON®-TB Gold test (QFT-G) and T-SPOT®.T.) This test, though, has not been validated in infants and young children so its use is limited.
In summary: the American Academy of Pediatrics and the Centers for Disease Control recommend:
• The tuberculin skin test (TST) of purified protein derivative is indicated for all children >3 months of age, regardless of their Bacille Calmette-Guérin (BCG) vaccination status.
• The TST should be interpreted regardless of their BCG vaccination status. - 10 mm of induration (hard lump under the skin) indicates exposure to tuberculosis (5 mm would be considered positive if there is a history of conact with active Tb, signs/symptoms of active Tb or having an active chest x-ray.)
• A chest radiograph and complete physical exam to assess for pulmonary and extrapulmonary tuberculosis are indicated for all children with positive TST results.
• Some experts recommend a repeat TST 3-6 months after arrival, feeling that malnutrition may supress the skin reaction.
• A child who has a positive TST but no evidence of active disease should be treated with isoniazid (antibiotic) for 9 months.
The term latent tuberculosis is used when the person is exposed to tuberculosis, has bacterium in their body but is not sick with disease. Fortunately this is the most common form among internationally adopted children rather than active tuberculosis.
For more information about tuberculosis: http://www.cdc.gov/TB/