Interpretation of repeat tuberculin skin testing in international adoptees: conversions or boosting

Tuberculosis prevention in children: a prospective community-based study in South Africa

Tuberculosis (TB) preventive therapy reduces TB risk in children. However, the effectiveness of TB preventive therapy in children living in high TB burden settings is unclear.

In a prospective observational community-based cohort study in Cape Town, South Africa, we assessed the effectiveness of routine TB preventive therapy in children ≤15 years of age in a high TB and HIV prevalence setting.

Among 966 children (median (interquartile range) age 5.07 (2.52–8.72) years), 676 (70%) reported exposure to an adult with TB in the past 3 months and 240 out of 326 (74%) eligible children initiated isoniazid preventive therapy under programmatic guidelines. Prevalent (n=73) and incident (n=27) TB were diagnosed among 100 out of 966 (10%) children. Children who initiated isoniazid preventive therapy were 82% less likely to develop incident TB than children who did not (adjusted OR 0.18, 95% CI 0.06–0.52; p=0.0014). Risk of incident TB increased if children were <5 years of age, living with HIV, had a positive Mycobacterium tuberculosis-specific immune response or recent TB exposure. The risk of incident TB was not associated with sex or Mycobacterium bovis bacille Calmette–Guérin vaccination status. Number needed to treat (NNT) was lowest in children living with HIV (NNT=15) and children <5 years of age (NNT=19) compared with children of all ages (NNT=82).

In communities with high TB prevalence, TB preventive therapy substantially reduces the risk of TB among children who are <5 years of age or living with HIV, especially those with recent TB exposure or a positive M. tuberculosis-specific immune response in the absence of disease.

In high TB burden communities, preventive therapy substantially reduces risk of TB among child contacts, especially those who are <5 years of age, living with HIV, recently TB exposed or have a positive M. tuberculosis-specific immune responsehttps://bit.ly/3dKHpUc

Low Prevalence of Tuberculin Skin Test Boosting among Community Residents in Uganda

Boosted tuberculin skin test (TST) reactions can be misclassified as new latent tuberculosis (TB) infection. To our knowledge, no study has evaluated the prevalence of TST boosting in a population-based sample in high TB burden settings. We determined the prevalence of TST boosting among urban residents in Uganda. We evaluated 99 participants with initial TST < 5 mm and repeated a skin test after 2 weeks. We found that only 2% had boosted TST reactions suggesting that most TST conversions could represent new TB infections in this high-burden setting.

Tuberculosis in Infants and Children

One million children develop tuberculosis disease each year, and 210,000 die from complications of tuberculosis. Childhood tuberculosis is very different from adult tuberculosis in epidemiology, clinical and radiographic presentation, and treatment. This review highlights the many unique features of childhood tuberculosis, with special emphasis on very young children and adolescents, who are most likely to develop disease after infection has occurred.

Relation between BCG vaccine scar and an interferon-gamma release assay in immigrant children with "positive" tuberculin skin test (≥10 mm)

Background

Immigrants from countries with high incidence of tuberculosis (TB) are usually offered screening when they arrive to low incidence countries. The tuberculin skin test (TST) is often used. The interferon gamma release assays (IGRAs) are more specific and not affected by BCG vaccination. The aims of this study were 1. To see if there if there is a correlation between a positive IGRA (QFT) and presence of a BCG scar in children with TST ≥10 mm, 2. To compare the TST diameter with QFT result, 3. To see if chest X-ray can be omitted in QFT negative children despite TST ≥10 mm.

Methods

762 healthy children/adolescents (median age 14 years) arriving to Gothenburg and surroundings with TST ≥10 mm were tested with QFT.

Results

A total of 163/492 (33 %) children with BCG scar had positive QFT, whereas 205/270 (76 %) without BCG scar had positive QFT (p < 0.0001). The median TST was 12 mm in QFT negative and 18 mm in QFT positive children (p < 0.0001) but with considerable overlap. Median TST was the same (12 mm) in QFT negative children with and without BCG scar. Among the QFT positive children 25/368 had chest X-ray changes compared to 2/393 among the QFT negative children (p < 0.0007).

Conclusions

Previous BCG vaccination had an effect on the TST diameter so an IGRA is recommended to diagnose latent TB. Using only TST for screening of latent TB would lead to overdiagnosis. The TST diameter was larger in QFT positive than in QFT negative children but could not predict QFT in the individual patient. Chest X ray contributes little to the diagnosis of TB in QFT negative children but can not be omitted because of late seroconversion of QFT in some patients.

Trial registration

Not applicable.

Dermatologic conditions in internationally adopted children

Over 200,000 children have been adopted into United States (US) families from abroad since the year 2000. Health care providers who care for children adopted internationally should be aware of the spectrum of illnesses seen in this population, and should be prepared to encounter potentially unusual situations. An appreciation for the unique pre-adoption exposures and vulnerabilities inherent in international adoption is critical for proper diagnosis and treatment of this heterogeneous group of children. It is important to consider the impact of potential early childhood stressors such as nutritional, sensory, and emotional deprivation, trauma and abuse, as well as prenatal exposures to drugs, alcohol, and infectious diseases. Providers must also take into account international variation in health care practices, including immunization, treatment, surgical, and hygiene standards. The differential diagnosis for cutaneous eruptions in children adopted internationally is broad and must encompass endemic systemic illnesses with skin manifestations, such as measles, tuberculosis, leprosy, and congenital syphilis, and primary dermatologic diseases such as scabies and bacterial and fungal infections. The importance of maintaining a broad differential and open mind when addressing the dermatologic needs of these children cannot be overemphasized.

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Dermatologists caring for children adopted internationally should be prepared for unusual situations.

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It is important to consider potential iatrogenic and infectious exposures, early physical and psychosocial stressors, and international variation in health care practices.

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The importance of maintaining a broad differential and open mind in these cases cannot be overemphasized.

The role of chest radiographs and tuberculin skin tests in tuberculosis screening of internationally adopted children

BACKGROUND

Internationally adopted children (IAC) are a growing group of US immigrants who often come from countries with high tuberculosis (TB) burdens. There is limited evidence to support current TB screening guidelines in these high-risk children. Therefore, we have prospectively examined the clinical utility of tuberculin skin testing (TST) and subsequent chest radiograph screening for TB disease in recently immigrated, asymptomatic IAC.

METHODS

Within 6 months of immigration to the United States, we collected demographic information and assessed the nutritional status of 566 IAC who presented for routine postadoptive care. Children completed standardized clinical examination and TSTs. Chest radiographs were recommended for children with TST induration ≥ 5 mm. The association between TST induration and clinical outcome was assessed. The clinical utility of chest radiographs was evaluated.

RESULTS

There was no difference in age, birth country, or nutritional status between IAC with TST induration of 0 to < 5 mm and those with 5 to < 10 mm; IAC with TST ≥ 10 mm were older, more chronically malnourished, and more likely to emigrate from Guatemala. Among children with TST ≥ 5 mm (35%), 4 IAC had chest radiographs which were initially interpreted to be abnormal and consistent with TB; ultimately none were diagnosed with TB.

CONCLUSIONS

The 5-mm TST cut point did not capture IAC with risk factors for latent TB infection or progression to TB disease, suggesting that this is not a useful screening threshold. In contrast, a 10-mm cut point identified IAC at risk for TB infection and therefore should be a more useful screening threshold. We question the clinical utility of radiographic screening for pulmonary TB in asymptomatic children.

Candida skin testing is a poor adjunct to tuberculin skin testing in international adoptees

We conducted a prospective longitudinal study evaluating Candida skin testing among international adoptees presenting to our clinic between 2000 and 2006. Nineteen (17%) and 17 (15%) children had negative tests at presentation and at 6 months, respectively--only 3 were negative at both points. Our study suggests that Candida skin test reactivity is an unstable measure of anergy among international adoptees.

T-cell interferon-gamma release assays for the rapid immunodiagnosis of tuberculosis: clinical utility in high-burden vs. low-burden settings

PURPOSE OF REVIEW

The utility of T-cell interferon-gamma (IFN-gamma) responses to Mycobacterium tuberculosis specific antigens [interferon-gamma release assays (IGRAs)] in high-burden settings remains unclear and there is growing evidence that IGRA performance varies across high tuberculosis (TB) burden vs. low TB burden settings. Here we review the evidence supporting the utility of IGRAs in specific subgroups and compare their performance in high-burden vs. low-burden settings.

RECENT FINDINGS

Although the IGRA, compared with the tuberculin skin test (TST), has greater specificity in BCG-vaccinated individuals, treatment of latent tuberculosis infection is not a priority in high-burden setting. Nevertheless, in high-burden settings, the TST performs reasonably well and correlates as well, or better, with proxy measures of exposure.

SUMMARY

IGRAs may still be useful in high-burden settings in specific subgroups at high risk of progression, including young children, HIV-infected individuals and healthcare workers, but this requires confirmation. Although the IGRAs cannot distinguish between latent and active TB, their utility as rule-out tests, when combined with smear microscopy or the TST, requires further study. Prospective studies are required in high-burden settings to confirm whether IFN-gamma responses are predictive of high risk of progression to active TB, particularly in HIV-infected individuals.