Tuberculosis Screening in Internationally Adopted Children: Test Twice
September 1, 2008
Tuberculosis Screening in Internationally Adopted Children: Test Twice
Abstract & Commentary
By Hal B. Jenson, MD, FAAP Professor of Pediatrics, Tufts University School of Medicine; Chief Academic Officer, Baystate Medical Center, Springfield, MA Dr. Jenson is on the speaker's bureau for Merck.
This article originally appeared in the August 2008 issue of Infectious Disease Alert.
Synopsis: A high proportion of internationally adopted children arriving in the United States have an initial false-positive tuberculin skin test. All internationally adopted children with an initially negative tuberculin skin test should have a repeat tuberculin skin test after three months in the United States. This should be the standard of care for identifying latent tuberculosis infection and preventing tuberculosis disease in these children.
Source: Trehan I, et al. Tuberculosis screening in internationally adopted children: The need for initial and repeat testing. Pediatrics. 2008;122:e7-e14.
A cohort of 549 internationally adopted children ≥ 3 months of age (mean age, 22.9 months; range, 1.2-200 months) was evaluated at Cincinnati Children's Hospital between 1999 and 2004, with a post-adoption health visit within two months (mean, 12 days) after arrival in the United States. Children arrived from 29 different countries, with 81% coming from Russia, China, Guatemala, Kazakhstan, and South Korea; none of the children tested positive for HIV infection.
The initial tuberculin skin test (TST) was read at 48-72 hours in 527 children (96%) and was positive (≥ 10 mm induration) in 111 children (21%). Of the 416 children with a negative initial TST, 92% had no induration and 8% had 1-9 mm of induration. In these 416 children, a second post-adoption TST was performed at least three months later in 203 children and read at 48-72 hours in 191 (94%). The repeat TST was positive in 38 children (20%). All of the children had normal physical examinations and chest radiographs and were diagnosed with latent tuberculosis infection (LTBI). They began the recommended nine-month course of isoniazid; there was no apparent association of positive repeat TST and country of birth.
The majority (81%) of children had evidence of BCG vaccination, except for children from South Korea, with only 15% having evidence of BCG vaccination. Only eight children had documentation of multiple BCG vaccinations. Children with evidence of BCG vaccination were more likely to have a positive TST result than children without evidence of BCG vaccination (OR: 15.3; 95% CI 3.3-70.1; p = 0.0004).
The median age (14.8 vs 13.1 months) and institutionalization history of children with a positive TST was not significantly different from children with a negative TST. The TST was positive 19.7% of the time for children who had lived in an orphanage or hospital at any time, 19.5% for children who had lived in an orphanage at least six months, and 24.1% for children who had resided in a foster home. Malnutrition (defined as a weight-for-age z score less than 2.0) was present in 158 (30%) children. The median (range) z score for children with a positive TST result, 1.13 (5.40-1.31), was slightly higher than for children with a negative TST result, 1.38 (7.00-3.94), p = 0.06. Children with an initially negative TST result were more likely to be malnourished compared to children with an initially positive TST result (31% vs 22%, p = 0.06).
Commentary
More than 20,000 children are adopted into the United States each year, many from areas of high tuberculosis endemicity. The initial health screening guidelines include testing for tuberculosis using the TST for all immigrants from high-prevalence countries. Consensus guidelines recommend that TST results be interpreted without consideration of the BCG vaccination history, and that the TST be repeated once the child is better nourished, if malnutrition is initially suspected.
Because of the long incubation period of tuberculosis infection, the TST has poor sensitivity following recent exposure and during early developing infection. Other factors that may contribute to anergy and false-negative TST results include undernourishment, recent live virus vaccine administration, concomitant infections, and immunosuppression.
Tuberculosis remains a major global public health threat. This study demonstrates that many additional cases of LTBI can be identified among internationally adopted children by repeat TST after a few months in the United States. It is unlikely that these children represent acquisition of tuberculosis infection in the United States, but rather that the ability to mount an appropriate delayed hypersensitivity response to TST occurs after nutritional status has improved. Although not statistically significant, the results of this study showed that malnourished children were less likely to have a positive TST result at the initial visit. A history of BCG vaccination is not a contraindication to placement of a TST, and the interpretation of the TST result should not be influenced by a history of BCG vaccination.
A cohort of 549 internationally adopted children ¡Ý 3 months of age (mean age, 22.9 months; range, 1.2-200 months) was evaluated at Cincinnati Children's Hospital between 1999 and 2004, with a post-adoption health visit within two months (mean, 12 days) after arrival in the United States.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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