Tuberculosis Screening in Immigrant Children
As defined by US immigration law, immigrants are persons lawfully admitted for permanent residence in the US. In 2000 alone 850,000 immigrants were granted legal permanent residence status including 152,000 <15 years old. This number does not include some migrants who are not counted as lawful permanent residents or illegal immigrants.
As the incidence of tuberculosis (TB) has decreased, the TB among foreign-born persons is of increasing importance. Throughout the 1990s the TB rate for foreign-born persons was at least 4-5 times that for US-born persons. The proportion of TB cases in foreign-born individuals increased to 42% in 1998.
Similarly foreign-born children have a much greater risk of latent tuberculosis infection (LTBI) than US-born peers. The prevalence of tuberculin reactivity in immigrant children is related to factors including country of origin, time since immigration, age of immigration, Calmette-Guérin bacillus (BCG) vaccination and socioeconomic status. Risk factors associated with LTBI vary according to prevalence of TB in the country of origin, thus highlighting that risk of TB and LTBI is not uniform among immigrants.
The Immigration and Naturalization Service requires that persons emigrating to the US complete evaluation. Local panel physicians designated by US embassies and consulates perform examinations that include (1) brief history of present and past illness, (2) a chest radiograph for TB in persons ≥15 years of age and (3) tuberculin skin test (TST) for those ≤15 years of age if the person is ill or has a family member with suspected TB. Consequently most immigrant children ≤15 years old receive neither TST nor chest radiograph as part of the immigration procedure. Thus local health departments and health care providers are charged with the responsibility of identifying and screening such children at high risk for LTBI.
The standard test for identification of TB infection is the Mantoux skin test with 5 tuberculin units of purified protein derivative. Studies fail to confirm the ability of parents and other laypersons to read the TST accurately. Health professionals trained in the ball-point technique should read all TSTs at 48-72 h. Additionally the use of calipers minimizes bias.
The use of the TST in BCG-vaccinated children creates significant confusion among providers. Receipt of BCG is not a contraindication for Mantoux testing, and a positive TST should not be attributed to BCG. Most foreign-born children received BCG vaccination as a newborn (WHO standard). No reliable method distinguishes between tuberculin reactions caused by BCG and those caused by mycobacterial infection. Although studies show that post-BCG-induced tuberculin reactivity ranges from 0- 19 mm of induration, this is generally <10 mm. A reaction ≥10 mm is unlikely 5 years or more after a single BCG during infancy and is unlikely to persist >10 years after vaccination in the absence of TB infection. If children receive BCG after 1 year of age or multiple BCG vaccinations, post-BCG TST reactivity may increase in size or persist longer. Additionally another BCG vaccination, recent TST or serial TSTs may lead to a booster reaction. Although variable definitions exist, a booster reaction may be defined as a reaction to a second TST of 10+ mm and exceeding the reaction to the first by at least 6 mm. Among foreign-born children a booster reaction is more likely due to a BCG vaccination that to LTBI.
Foreign-born children should receive a TST on arrival to the US if at risk for LTBI. Risk assessment of LTBI in immigrant children should be based on locally developed epidemiologic profiles identifying groups of foreign-born persons at risk for TB. In the absence of such data, children from low burden countries without other risk factors for LTBI do not need TST testing. In a BCG-vaccinated foreign-born child from a low burden country with no specific risk factors, TST reaction <10 mm is most likely caused by prior BCG. In contrast in a BCG-vaccinated foreign-born child from a high burden country or with specific risk factors. TST reaction >10 mm most likely indicates LTBI. All foreign-born children from high burden countries or with significant risk of LTBI should have a TST soon after arrival to the US. Countries with annual TB incidence of <40 per 100,000 are considered low; countries with annual incidence of >100 per 100,000 are considered high; and the incidence is intermediate between these levels. Foreign-born children should have future TSTs when they have ongoing risk of LTBI, such as travel to high burden countries and/or significant contact with indigenous persons from such countries, exposure to high risk persons (migrant farm workers, HIV-infected, homeless, users of illicit drugs, residents of nursing homes, institutions or prisons) or residence in high prevalence areas.
Some foreign-born children may have received BCG recently or a TST shortly before immigration. Recent BCG or TST may boost the host response to a subsequent TST. Therefore if children have documentation of a recent TST or evidence of recent BCG, clinicians may consider postponing the TST. The benefits of postponing the TST must be weighed against the risks, of TB, LTBI and losing the child to follow-up. The TST should not be deferred in children with illness, abnormal chest radiographs or in family members of close contacts with TB.
Foreign-born adoptees present a unique challenge to providers. They have a compounded risk of LTBI related to factors including high burden birth countries, institutional living, poor access to medical care and close contact with caretakers with high rates of infection. Studies have reported rates up to 10-20% in foreign-born adoptees. In addition these children suffer high rates of malnutrition, placing them at risk for progression of LTBI and anergy to TST. Because of their significant risk of LTBI, foreign-born adoptees should receive TST in the immediate postadoptive period. Additionally some recommend anergy testing. All experts recommend repeat TST 6 months postadoption because of the risk of infection occurring just before adoption with TST positivity developing several weeks or months postadoption. In general 10 mm is the cut point for LTBI in these children. In a child with a TST reaction ≥5 mm and multiple risk factors for LTBI or clinical suspicion of disease, clinicians should obtain a chest radiograph to rule out pulmonary TB.
Refugee children are at significant risk of LTBI compared with the general immigrant population. Studies have identified higher rates of TB among refugees and internally displaced persons than among the general population in their country of origin and the general immigrant population. When possible, screening protocols should be tailored to the specific risk of the refugee population. For example the CDC recommends for Southeast Asian refugee children 2-14 years old a modified TB screening procedure that includes a chest radiograph.
TB drug resistance rates are higher among foreign-born than US-born populations. Thus foreign-born children are at significant risk of exposure to LTBI caused by isoniazid-resistant M. tuberculosis. In most cases it is impossible to discover the child's source case and the drug susceptibility of his isolate. In general foreign-born children with LTBI should be treated with isoniazid unless there are specific data linking the child to a known case of isoniazid-resistant tuberculosis.
In summary foreign-born children have a much greater risk of LTBI than US-born peers. Local health departments and healthcare providers are responsible for identifying and screening these children. Effective and timely identification, screening and treatment not only improves long term health outcomes for immigrant children but is also consonant with public health imperatives.
As defined by US immigration law, immigrants are persons lawfully admitted for permanent residence in the US. In 2000 alone 850,000 immigrants were granted legal permanent residence status including 152,000 <15 years old. This number does not include some migrants who are not counted as lawful permanent residents or illegal immigrants.
As the incidence of tuberculosis (TB) has decreased, the TB among foreign-born persons is of increasing importance. Throughout the 1990s the TB rate for foreign-born persons was at least 4-5 times that for US-born persons. The proportion of TB cases in foreign-born individuals increased to 42% in 1998.
Similarly foreign-born children have a much greater risk of latent tuberculosis infection (LTBI) than US-born peers. The prevalence of tuberculin reactivity in immigrant children is related to factors including country of origin, time since immigration, age of immigration, Calmette-Guérin bacillus (BCG) vaccination and socioeconomic status. Risk factors associated with LTBI vary according to prevalence of TB in the country of origin, thus highlighting that risk of TB and LTBI is not uniform among immigrants.
The Immigration and Naturalization Service requires that persons emigrating to the US complete evaluation. Local panel physicians designated by US embassies and consulates perform examinations that include (1) brief history of present and past illness, (2) a chest radiograph for TB in persons ≥15 years of age and (3) tuberculin skin test (TST) for those ≤15 years of age if the person is ill or has a family member with suspected TB. Consequently most immigrant children ≤15 years old receive neither TST nor chest radiograph as part of the immigration procedure. Thus local health departments and health care providers are charged with the responsibility of identifying and screening such children at high risk for LTBI.
The standard test for identification of TB infection is the Mantoux skin test with 5 tuberculin units of purified protein derivative. Studies fail to confirm the ability of parents and other laypersons to read the TST accurately. Health professionals trained in the ball-point technique should read all TSTs at 48-72 h. Additionally the use of calipers minimizes bias.
The use of the TST in BCG-vaccinated children creates significant confusion among providers. Receipt of BCG is not a contraindication for Mantoux testing, and a positive TST should not be attributed to BCG. Most foreign-born children received BCG vaccination as a newborn (WHO standard). No reliable method distinguishes between tuberculin reactions caused by BCG and those caused by mycobacterial infection. Although studies show that post-BCG-induced tuberculin reactivity ranges from 0- 19 mm of induration, this is generally <10 mm. A reaction ≥10 mm is unlikely 5 years or more after a single BCG during infancy and is unlikely to persist >10 years after vaccination in the absence of TB infection. If children receive BCG after 1 year of age or multiple BCG vaccinations, post-BCG TST reactivity may increase in size or persist longer. Additionally another BCG vaccination, recent TST or serial TSTs may lead to a booster reaction. Although variable definitions exist, a booster reaction may be defined as a reaction to a second TST of 10+ mm and exceeding the reaction to the first by at least 6 mm. Among foreign-born children a booster reaction is more likely due to a BCG vaccination that to LTBI.
Foreign-born children should receive a TST on arrival to the US if at risk for LTBI. Risk assessment of LTBI in immigrant children should be based on locally developed epidemiologic profiles identifying groups of foreign-born persons at risk for TB. In the absence of such data, children from low burden countries without other risk factors for LTBI do not need TST testing. In a BCG-vaccinated foreign-born child from a low burden country with no specific risk factors, TST reaction <10 mm is most likely caused by prior BCG. In contrast in a BCG-vaccinated foreign-born child from a high burden country or with specific risk factors. TST reaction >10 mm most likely indicates LTBI. All foreign-born children from high burden countries or with significant risk of LTBI should have a TST soon after arrival to the US. Countries with annual TB incidence of <40 per 100,000 are considered low; countries with annual incidence of >100 per 100,000 are considered high; and the incidence is intermediate between these levels. Foreign-born children should have future TSTs when they have ongoing risk of LTBI, such as travel to high burden countries and/or significant contact with indigenous persons from such countries, exposure to high risk persons (migrant farm workers, HIV-infected, homeless, users of illicit drugs, residents of nursing homes, institutions or prisons) or residence in high prevalence areas.
Some foreign-born children may have received BCG recently or a TST shortly before immigration. Recent BCG or TST may boost the host response to a subsequent TST. Therefore if children have documentation of a recent TST or evidence of recent BCG, clinicians may consider postponing the TST. The benefits of postponing the TST must be weighed against the risks, of TB, LTBI and losing the child to follow-up. The TST should not be deferred in children with illness, abnormal chest radiographs or in family members of close contacts with TB.
Foreign-born adoptees present a unique challenge to providers. They have a compounded risk of LTBI related to factors including high burden birth countries, institutional living, poor access to medical care and close contact with caretakers with high rates of infection. Studies have reported rates up to 10-20% in foreign-born adoptees. In addition these children suffer high rates of malnutrition, placing them at risk for progression of LTBI and anergy to TST. Because of their significant risk of LTBI, foreign-born adoptees should receive TST in the immediate postadoptive period. Additionally some recommend anergy testing. All experts recommend repeat TST 6 months postadoption because of the risk of infection occurring just before adoption with TST positivity developing several weeks or months postadoption. In general 10 mm is the cut point for LTBI in these children. In a child with a TST reaction ≥5 mm and multiple risk factors for LTBI or clinical suspicion of disease, clinicians should obtain a chest radiograph to rule out pulmonary TB.
Refugee children are at significant risk of LTBI compared with the general immigrant population. Studies have identified higher rates of TB among refugees and internally displaced persons than among the general population in their country of origin and the general immigrant population. When possible, screening protocols should be tailored to the specific risk of the refugee population. For example the CDC recommends for Southeast Asian refugee children 2-14 years old a modified TB screening procedure that includes a chest radiograph.
TB drug resistance rates are higher among foreign-born than US-born populations. Thus foreign-born children are at significant risk of exposure to LTBI caused by isoniazid-resistant M. tuberculosis. In most cases it is impossible to discover the child's source case and the drug susceptibility of his isolate. In general foreign-born children with LTBI should be treated with isoniazid unless there are specific data linking the child to a known case of isoniazid-resistant tuberculosis.
In summary foreign-born children have a much greater risk of LTBI than US-born peers. Local health departments and healthcare providers are responsible for identifying and screening these children. Effective and timely identification, screening and treatment not only improves long term health outcomes for immigrant children but is also consonant with public health imperatives.
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