Language: English Spanish. A cohort of 1, children household contacts of adults with smear-positive pulmonary tuberculosis was followed up for 24 months. Study period The incidence rate of active tuberculosis was There is a need for prompt interruption of adult-to-children tuberculosis transmission within households. Conducting proper contact investigation and offering chemoprophylaxis to infected children could reduce tuberculosis transmission.

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Language: English Spanish. A cohort of 1, children household contacts of adults with smear-positive pulmonary tuberculosis was followed up for 24 months. Study period The incidence rate of active tuberculosis was There is a need for prompt interruption of adult-to-children tuberculosis transmission within households. Conducting proper contact investigation and offering chemoprophylaxis to infected children could reduce tuberculosis transmission.

Periodo de estudio La tasa de incidencia de tuberculosis activa fue de Tuberculosis in children is considered a public health emergency that affects mainly low-income countries 1. The pathogenesis and epidemiology of childhood tuberculosis are still poorly understood, possibly because most of the actions in tuberculosis prevention, diagnostic, and therapeutic options are focused mainly on adults 1. Further, there are surveillance gaps. In Colombia, 16, new tuberculosis cases were estimated in , Tracing contacts of patients with microbiologically confirmed tuberculosis is one of the main strategies to control this disease.

This strategy has proved to be cost-effective for the detection of new cases 9 when combined with the required access to diagnosis and treatment Children household contacts of adult tuberculosis patients who become infected but do not develop active childhood tuberculosis primary tuberculosis , represent the main reservoir for tuberculosis transmission once reactivation occurs in adulthood post-primary tuberculosis 1.

In a given community, a decrease in the number of children with active tuberculosis is an indicator of transmission decrease because they usually get infected within the nuclear family Also, the proportion of children with tuberculosis infection is estimated at This resulted in a sample size of 2, household contacts of all ages.

A child household contact was defined as an individual who had spent time regularly every week with an index case in the same household, for at least one month before the confirmation of the tuberculosis case. An index case was defined as the first tuberculosis case identified in each household, diagnosed with active pulmonary, smear-positive tuberculosis. Adapted from CDC Recruitment conditions for index cases and children household contacts were the same for all cities, as previously published about Medellin Briefly, once an adult case was notified to the local tuberculosis control program, the patient and children household contacts were invited to participate in the study, followed by the signature of informed consent.

After index cases were identified and they approved a first baseline visit, the research team went to the household to explain the study and obtain written informed consent from parents or responsible adult guardians, to collect socio-demographic and exposure information, and to perform the tuberculin skin test. Follow-up occurred throughout visits every six months and telephone calls every three months.

The total follow-up time was at least 24 months. Also, local epidemiological surveillance databases were checked for active tuberculosis cases reported. Following the recommendations of the American Thoracic Society 20 , an analysis of tuberculin skin test positivity using a cutoff of 5 mm of induration was also included. The annual risk of infection was determined through the tuberculin skin test conversion of a child household contact with a negative tuberculin skin test at baseline.

The conversion was defined as an increase of at least 6 mm of induration a year after the initial test Socioeconomic strata were recorded according to classifications used by local public services provider and categorized as low socioeconomic strata yes or not.

Proximity to the index case was classified as follows: children household contacts slept in other households, children household contacts slept in the same household, children household contacts slept in the same room. Crowding was considered when three or more persons shared the same bedroom Having other relatives with tuberculosis was defined as an additional contact with a tuberculosis case besides the index case. Evaluation of children in Cali was performed through a diagnostic algorithm Social, demographic and clinical characteristics, as well as the degree of proximity to the index case, were compared using the distribution of absolute and relative frequencies.

Adjusted PR was estimated using binomial regression. HR was adjusted by a Cox regression. The Kaplan-Meir method was used to estimate time to the disease for each age group. Analyses were done using Stata This study, including the informed consent used, was approved by the Ethical Committee of Facultad de Medicina, Universidad de Antioquia, and it applied for each city. The study was also supported by the National Tuberculosis Program and the regional public health authorities. Most children involved in the study did not receive isoniazid preventive therapy because the majority were vaccinated.

Active tuberculosis cases received tuberculosis treatment according to National Tuberculosis Program. The demographic and epidemiological characteristics of the 1, children included in this study are shown in Table 1. Most children belonged to low socioeconomic strata From the whole cohort, 1. The same factors showed a similar trend, although not significant when a cutoff point of 5 mm was applied Table 2.

A significant correlation was found between M. TST: Tuberculin skin Test. HHC: household contact. Nineteen children developed active tuberculosis during follow-up 7. Figure 1 shows the number of children who developed active tuberculosis according to the result of the initial tuberculin skin test and the increase of tuberculin skin test induration per year. The general incidence rate for active tuberculosis was Also, a positive association was found between crowding and the early development of active tuberculosis, but it was not significant when the BCG scar was considered.

A systematic review and meta-analysis of the evidence on the yield of household contact investigations in countries with similar epidemiological characteristics than Colombia, found a prevalence of tuberculosis infection of Additionally, the incidence rate of infection after one year of follow-up was high, suggesting that a significant risk for developing active tuberculosis persists after one year.

Usually, it is calculated from the observed infection prevalence in scholar age children, given that even in places where a high transmission occurs, measurement of infection by using tuberculin skin test sequentially will require significant sample sizes, and the results may be influenced by booster effects 27 - Performing annual tuberculin skin test, our study showed that annual risk of infection in children household contacts of adults with pulmonary tuberculosis is higher than the one reported in general population in Russia with a moderate disease incidence annual risk of infection in 0.

In contrast, in two countries with high tuberculosis incidence as Zambia and South Africa, the reported annual risk of infection in children between years old was 2. These studies differ from our study in the way the annual risk of infection was calculated estimated from data obtained with prevalence surveys and in the cutoff point for considering a positive tuberculin skin test; even though, our data support that the infection risk for tuberculosis remains greater in children household contacts of patients with active tuberculosis annual risk of infection The risk of developing active tuberculosis decreases with age, and the protective effect of BCG vaccination for infection, active tuberculosis, and severe disease have been reported 25 , 33 , 37 using interferon-gamma as an infection marker However, these effects vary in different geographical regions, which could be related to the genetic dependent immune response that affects even tuberculin skin test results Although tuberculin skin test is widely used to determine infection by M.

Its specificity is poor in BCG vaccinated populations, it has cross-reactivity with non-tuberculous mycobacteria and its sensitivity decrease in immunocompromised patients 25 , 40 , These tuberculin skin test characteristics may have a confusing effect, especially in the association found between the presence of BCG vaccination scar and the prevalence of tuberculosis infection.

The present study is the first in our country with these characteristics, which includes the follow-up of a cohort of children exposed to tuberculosis. That suggests a weakness in the country activities for identification of children with disease Children included in the study were part of a cohort of household contacts of patients with pulmonary tuberculosis.

Thus the initial sample size was not calculated exclusively for children. A similar result was obtained for comparison of active tuberculosis incidence rate according to the presence or not presence of crowding.

Besides, the estimated tuberculosis annual risk of infection is not comparable to traditional methods used. Currently tuberculosis contact tracing with tuberculin skin test is complemented with commercial interferon-gamma release assay, even in children, results from in-house interferon-gamma quantification were reported previously The authors would like to thank the supporters, the patients, their household contacts, and the tuberculosis program officials.

The physicians, the nurses, and technicians, and the rest of the staff that made this study possible. Financial sponsors did not participate in study design, data collection, and analysis or decisions related to writing and publishing the manuscript.

En Colombia, se estimaron 16, casos nuevos de tuberculosis en , el Adaptado del CDC El seguimiento total fue de al menos 24 meses. Se consideraron significativos aquellos valores-p menores a 0. Los casos de tuberculosis activa recibieron tratamiento para tuberculosis de acuerdo con el Programa Nacional de Tuberculosis.

Fueron Del total de la cohorte, se retiraron voluntariamente del estudio el 1. TST: Prueba de tuberculina. La tasa de incidencia de tuberculosis activa en general fue de Su especificidad es pobre en poblaciones vacunadas con BCG, tiene reactividad cruzada con micobacterias no tuberculosas y su sensibilidad disminuye en pacientes inmunocomprometidos 25 , 40 , Los autores agradecen a los financiadores, a los pacientes y a sus convivientes, y a los funcionarios del programa de tuberculosis.

National Center for Biotechnology Information , U. Journal List Colomb Med Cali v. Colomb Med Cali. Published online Dec Find articles by Dione Benjumea-Bedoya. Find articles by Jaime Robledo. Find articles by Luis F Barrera. Find articles by Helena del Corral. Find articles by Beatriz E Ferro. Find articles by Sonia L Villegas. Find articles by Carlos A Rojas. Author information Article notes Copyright and License information Disclaimer.


Risk of infection and disease progression in children exposed to tuberculosis at home, Colombia

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