Browsing by Author "Castellanos, Maria Eugenia"

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    Defining an intermediate category of tuberculin skin test: A mixture model analysis of two high-risk populations from Kampala, Uganda
    (Creative Commons Attribution License, 2021) Woldu, Henok G.; Zalwango, Sarah; Martinez, Leonardo; Castellanos, Maria Eugenia; Kakaire, Robert; Sekandi, Juliet N.; Kiwanuka, Noah; Whalen, Christopher C.
    One principle of tuberculosis control is to prevent the development of tuberculosis disease by treating individuals with latent tuberculosis infection. The diagnosis of latent infection using the tuberculin skin test is not straightforward because of concerns about immunologic cross reactivity with the Bacille Calmette-Guerin (BCG) vaccine and environmental mycobacteria. To parse the effects of BCG vaccine and environmental mycobacteria on the tuberculin skin test, we estimated the frequency distribution of skin test results in two divisions of Kampala, Uganda, ten years apart. We then used mixture models to estimate parameters for underlying distributions and defined clinically meaningful criteria for latent infection, including an indeterminate category. Using percentiles of two underlying normal distributions, we defined two skin test readings to demarcate three ranges. Values of 10 mm or greater contained 90% of individuals with latent infection; values less than 7.2 mm contained 80% of individuals without infection. Contacts with values between 7.2 and 10 mm fell into an indeterminate zone where it was not possible to assign infection. We conclude that systematic tuberculin skin test surveys within populations at risk, combined with mixture model analysis, may be a reproducible, evidence-based approach to define meaningful criteria for latent tuberculosis infection.
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    Excess Risk of Tuberculosis Infection Among Extra-household Contacts of Tuberculosis Cases in an African City
    (Clinical Infectious Diseases, 2021) Kakaire, Robert; Kiwanuka, Noah; Zalwango, Sarah; Sekandi, Juliet N.; Quach, Trang Ho Thu; Castellanos, Maria Eugenia; Quinn, Frederick; Whalen, Christopher C.
    Although households of tuberculosis (TB) cases represent a setting for intense transmission of Mycobacterium tuberculosis, household exposure accounts for <20% of transmission within a community. The aim of this study was to estimate excess risk of M. tuberculosis infection among household and extra-household contacts of index cases. Methods. We performed a cross-sectional study in Kampala, Uganda, to delineate social networks of TB cases and matched controls without TB. We estimated the age-stratified prevalence difference of TB infection between case and control networks, partitioned as household and extra-household contacts. Results. We enrolled 123 index cases, 124 index controls, and 2415 first-degree network contacts. The prevalence of infection was highest among household contacts of cases (61.5%), lowest among household contacts of controls (25.2%), and intermediary among extra-household TB contacts (44.9%) and extra-household control contacts (41.2%). The age-adjusted prevalence difference between extra-household contacts of cases and their controls was 5.4%. The prevalence of infection was similar among the majority of extra-household case contacts and corresponding controls (47%). Conclusions. Most first-degree social network members of TB cases do not have adequate contact with the index case to experience additional risk for infection, but appear instead to acquire infection through unrecognized exposures with infectious cases in the community.
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    Performance of a Score to Characterize Adequate Contact among the Social Network of Persons with Tuberculosis
    (Research Square, 2021) Castellanos, Maria Eugenia; Zalwango, Sarah; Quach, Trang; Kakaire, Robert; Martínez, Leonardo; Ebell, Mark H.; Dobbin, Kevin K.; Kiwanuka, Noah; Whalen, Christopher C.
    Exposure to an individual with tuberculosis is necessary for transmission to occur. Previously, we developed a score that measures contact between tuberculosis cases and their social networks in an African urban context. This score was built using exploratory factor analysis and identified contact as the conjunction of two domains – setting and relationship. Now, our aim is to determine whether this score covaries with the presence of tuberculous infection among social contacts of tuberculosis cases.