M. tuberculosis Infection Attributable to Exposure in Social Networks of Tuberculosis Cases in an Urban African Community

Background

The persistence of tuberculosis today and its global disparity send a powerful message that effective tuberculosis control must respond to its regional epidemiology. Active case finding through contact investigation is a standard protocol used for tuberculosis control, but its effectiveness has not been established, especially in endemic areas.

Methods

To quantify the potential effectiveness of contact investigation in Kampala, Uganda, we used a cross-sectional design to evaluate the social networks of 123 tuberculosis index cases and 124 controls without tuberculosis.

Results

Tuberculous infection was present in 515 of 989 tuberculosis case contacts (52.1%) and 396 of 1026 control contacts (38.6%; adjusted prevalence ratio, 1.4; 95% CI, 1.3-1.6). The proportion of infected participants with known exposure within the social network of the tuberculosis case was 35%. The population-attributable fraction was 11.1% for any known exposure, with 7.3% attributable to household exposure and 3.4% attributable to extrahousehold exposure.

Conclusions

This low population-attributable fraction indicates that contact tracing in the social networks of index cases will have only a modest effect in reducing tuberculous infection in a community. New approaches to community-level active case finding are needed.

Stigma and Associated Sex Disparities Among Patients with Tuberculosis in Uganda: A Cross-Sectional Study

Background

Tuberculosis (TB) is one of the leading causes of death from a single infectious agent globally. Stigma associated with TB encompassing self-, anticipated-, and public-stigma has significant negative effects on treatment adherence. In Uganda, limited data exist on the prevalence of stigma and its relationship with sex among patients with TB. We evaluate prevalence of three types of stigma and their relationship with the sex of patients undergoing TB treatment.

Methods

This cross-sectional study was conducted between July 2020 to March 2021 at selected TB clinics in Kampala, Uganda. Eligible participants were aged 18-65 with confirmed TB and starting their prescribed treatment. We collected data on socio-demographics and used 13 items to capture the self-, anticipated-, and public-stigma from which we composed the dependent variables. The primary independent variable was sex. We employed multivariable logistic regression analysis to evaluate the association between sex and the three stigma types. Additionally, we considered potential confounders such as age, HIV, and employment status. Statistical significance was defined as p<0.05.

Results

In this study we enrolled 144 participants with a mean age of 35.8 years (standard deviation = 12). Half of the participants (50%, n=72) were female, 44% had a secondary education, 37.5% were unemployed, and 32.6% were co-infected with HIV. The prevalence of self-stigma was 71.1%, anticipated stigma was 75.7%, and public stigma was 41.7%. Significant factors were associated with self-stigma were female sex (adjusted odds ratio (AOR): 2.35 95% CI: 1.02-5.74) and unemployment (AOR: 2.95 95% CI: 1.16-8.58). HIV-positive status was significantly associated with anticipated stigma (AOR: 3.58 95% CI: 1.38-11.23). However, none of the variables we evaluated showed a significant association with public stigma.

Conclusions

Our study showed a high prevalence of self, anticipated and public stigma among TB patients. Notably, females and unemployed individuals were at a higher risk of self-stigma, while those with HIV/AIDS and TB were more likely to report anticipated stigma. To combat stigma effectively, interventions should be tailored to cater to sex-specific needs and persons living with HIV. Future research should delve further in determinants of TB-related stigma in high-burden settings.

Acceptability, Usefulness, and Ease of Use of an Enhanced Video Directly Observed Treatment System for Supporting Patients With Tuberculosis in Kampala, Uganda: Explanatory Qualitative Study

BACKGROUND

In tuberculosis (TB) control, nonadherence to treatment persists as a barrier. The traditional method of ensuring adherence, that is, directly observed therapy, faces significant challenges that hinder its widespread adoption. Digital adherence technologies such as video directly observed therapy (VDOT) are emerging as promising solutions. However, as these novel technologies gain momentum, a critical gap is the lack of comprehensive studies evaluating their efficacy and the unique experiences of patients in Africa.

OBJECTIVE

The aim of this study was to assess patients' experiences that affected acceptability, usefulness, and ease of use with an enhanced VDOT system during monitoring of TB treatment.

METHODS

We conducted individual open-ended interviews in a cross-sectional exit qualitative study in Kampala, Uganda. Thirty participants aged 18-65 years who had completed the VDOT randomized trial were purposively selected to represent variability in sex, adherence level, and HIV status. We used a hybrid process of deductive and inductive coding to identify content related to the experience of study participation with VDOT. Codes were organized into themes and subthemes, which were used to develop overarching categories guided by constructs adapted from the modified Technology Acceptance Model for Resource-Limited Settings. We explored participants' experiences regarding the ease of use and usefulness of VDOT, thereby identifying the facilitators and barriers to its acceptability. Perceived usefulness refers to the benefits users expect from the technology, while perceived ease of use refers to how easily users navigate its various features. We adapted by shifting from assessing perceived to experienced constructs.

RESULTS

The participants' mean age was 35.3 (SD 12) years. Of the 30 participants, 15 (50%) were females, 13 (43%) had low education levels, and 22 (73%) owned cellphones, of which 10 (45%) had smartphones. Nine (28%) were TB/HIV-coinfected, receiving antiretroviral therapy. Emergent subthemes for facilitators of experienced usefulness and ease of VDOT use were SMS text message reminders, technology training support to patients by health care providers, timely patient-provider communication, family social support, and financial incentives. TB/HIV-coinfected patients reported the added benefit of adherence support for their antiretroviral medication. The external barriers to VDOT's usefulness and ease of use were unstable electricity, technological malfunctions in the app, and lack of cellular network coverage in rural areas. Concerns about stigma, disease disclosure, and fear of breach in privacy and confidentiality affected the ease of VDOT use.

CONCLUSIONS

Overall, participants had positive experiences with the enhanced VDOT. They found the enhanced VDOT system user-friendly, beneficial, and acceptable, particularly due to the supportive features such as SMS text message reminders, incentives, technology training by health care providers, and family support. However, it is crucial to address the barriers related to technological infrastructure as well as the privacy, confidentiality, and stigma concerns related to VDOT.

Vitamin D and Probability of Developmental Disorders among Perinatally HIV-Affected and Unaffected Ugandan Children

We tested the hypothesis that vitamin D deficiency (VDD) is associated with higher developmental disorder probability in 604 children with perinatal HIV infection (CPHIV, n = 199), HIV exposed and uninfected (CHEU, n = 196), and HIV unexposed uninfected (CHUU, n = 201). Children at 6-18 years old and their adult caregivers were assessed at enrollment, 6, and 12-month follow-ups. Serum 25-hydroxyvitamin-D (25OHD) levels in children quantified per the NHANES protocol were used to define VD categories as VDD (25OHD < 20 ng/mL), VD insufficient (VDI, 20 ≤ 25OHD ≤ 25 ng/mL), and VD sufficient (VDS = reference group if 25OHD > 25 ng/mL). Perinatal HIV status per DNA polymerase chain reaction/HIV rapid diagnostic tests included: CPHIV, CHEU, and CHUU. Developmental stage was defined as pre-adolescent (age < 11) vs. adolescent (age ≥ 11) years. Caregiver responses to standardized questions from Behavioral Assessment System for Children, Third Edition (BASC-3), were used to calculate probability scores for four disorders, namely: autism (ASD), attention deficit & hyperactivity (ADHD), emotional behavioral disorder (EBD), functional impairment (FI), and resiliency at 0, 6 and 12 months. Multivariable longitudinal models estimated VD-associated standardized mean difference (SMD) and corresponding 95% confidence intervals (95% CI) in respective probability scores in Statistical Analysis Software (v.9.4). Baseline VDD vs. VDS predicted higher probability scores of moderate clinical importance for ASD, ADHD, EBD, and higher FI among pre-adolescents (SMD = 0.32 to 0.40, 95% CI: 0.00 to 0.74). VDD was not associated with resiliency or any developmental disorders among adolescents. VDD predicted higher developmental disorder and FI scores over 12 months in a developmental stage-dependent manner. This relationship requires further understanding to appropriately target future interventions.

Stakeholders' Perceptions of Benefits of and Barriers to Using Video-Observed Treatment for Monitoring Patients With Tuberculosis in Uganda: Exploratory Qualitative Study

Background

Nonadherence to treatment remains a barrier to tuberculosis (TB) control. Directly observed therapy (DOT) is the standard for monitoring adherence to TB treatment worldwide, but its implementation is challenging, especially in resource-limited settings. DOT is labor-intensive and inconvenient to both patients and health care workers. Video DOT (VDOT) is a novel patient-centered alternative that uses mobile technology to observe patients taking medication remotely. However, the perceptions and acceptability of potential end users have not been evaluated in Africa.

Objective

This study explores stakeholders’ acceptability of, as well as perceptions of potential benefits of and barriers to, using VDOT to inform a pilot study for monitoring patients with TB in urban Uganda.

Methods

An exploratory, qualitative, cross-sectional study with an exit survey was conducted in Kampala, Uganda, from April to May 2018. We conducted 5 focus group discussions, each comprising 6 participants. Groups included patients with TB (n=2 groups; male and female), health care providers (n=1), caregivers (n=1), and community DOT volunteer workers (n=1). The questions that captured perceived benefits and barriers were guided by domains adopted from the Technology Acceptance Model. These included perceived usefulness, ease of use, and intent to use technology. Eligible participants were aged ≥18 years and provided written informed consent. For patients with TB, we included only those who had completed at least 2 months of treatment to minimize the likelihood of infection. A purposive sample of patients, caregivers, health care providers, and community DOT workers was recruited at 4 TB clinics in Kampala. Trained interviewers conducted unstructured interviews that were audio-recorded, transcribed, and analyzed using inductive content analysis to generate emerging themes.

Results

The average age of participants was 34.5 (SD 10.7) years. VDOT was acceptable to most participants on a scale of 1 to 10. Of the participants, 70% (21/30) perceived it as highly acceptable, with scores ≥8, whereas 30% (9/30) scored between 5 and 7. Emergent themes on perceived benefits of VDOT were facilitation of easy adherence monitoring, timely follow-up on missed doses, patient-provider communication, and saving time and money because of minimal travel to meet in person. Perceived barriers included limited technology usability skills, inadequate cellular connectivity, internet access, availability of electricity, cost of the smartphone, and use of the internet. Some female patients raised concerns about the disruption of their domestic work routines to record videos. The impact of VDOT on privacy and confidentiality emerged as both a perceived benefit and barrier.

Conclusions

VDOT was acceptable and perceived as beneficial by most study participants, despite potential technical and cost barriers. Mixed perceptions emerged about the impact of VDOT on privacy and confidentiality. Future efforts should focus on training users, ensuring adequate technical infrastructure, assuring privacy, and performing comparative cost analyses in the local context.

Association between tuberculosis in men and social network structure in Kampala, Uganda

Background

Globally, tuberculosis disease (TB) is more common among males than females. Recent research proposes that differences in social mixing by sex could alter infection patterns in TB. We examine evidence for two mechanisms by which social-mixing could increase men’s contact rates with TB cases. First, men could be positioned in social networks such that they contact more people or social groups. Second, preferential mixing by sex could prime men to have more exposure to TB cases.

Methods

We compared the networks of male and female TB cases and healthy matched controls living in Kampala, Uganda. Specifically, we estimated their positions in social networks (network distance to TB cases, degree, betweenness, and closeness) and assortativity patterns (mixing with adult men, women, and children inside and outside the household).

Results

The observed network consisted of 11,840 individuals. There were few differences in estimates of node position by sex. We found distinct mixing patterns by sex and TB disease status including that TB cases have proportionally more adult male contacts and fewer contacts with children.

Conclusions

This analysis used a network approach to study how social mixing patterns are associated with TB disease. Understanding these mechanisms may have implications for designing targeted intervention strategies in high-burden populations.

Assessing a transmission network of Mycobacterium tuberculosis in an African city using single nucleotide polymorphism threshold analysis

Tuberculosis (TB) is the leading cause of death in humans by a single infectious agent worldwide with approximately two billion humans latently infected with the bacterium Mycobacterium tuberculosis. Currently, the accepted method for controlling the disease is Tuberculosis Directly Observed Treatment Shortcourse (TB-DOTS). This program is not preventative and individuals may transmit disease before diagnosis, thus better understanding of disease transmission is essential. Using whole-genome sequencing and single nucleotide polymorphism analysis, we analyzed genomes of 145 M. tuberculosis clinical isolates from active TB cases from the Rubaga Division of Kampala, Uganda. We established that these isolates grouped into M. tuberculosis complex (MTBC) lineages 1, 2, 3, and 4, with the most isolates grouping into lineage 4. Possible transmission pairs containing ≤12 SNPs were identified in lineages 1, 3, and 4 with the prevailing transmission in lineages 3 and 4. Furthermore, investigating DNA codon changes as a result of specific SNPs in prominent virulence genes including plcA and plcB could indicate potentially important modifications in protein function. Incorporating this analysis with corresponding epidemiological data may provide a blueprint for the integration of public health interventions to decrease TB transmission in a region.

Defining an intermediate category of tuberculin skin test: A mixture model analysis of two high-risk populations from Kampala, Uganda

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.

Using a Mobile Health Intervention (DOT Selfie) With Transfer of Social Bundle Incentives to Increase Treatment Adherence in Tuberculosis Patients in Uganda: Protocol for a Randomized Controlled Trial

Background

The World Health Organization’s End TB Strategy envisions a world free of tuberculosis (TB)—free of deaths, disease, and suffering due to TB—by 2035. Nonadherence reduces cure rates, prolongs infectiousness, and contributes to the emergence of multidrug-resistant TB (MDR-TB). Moreover, MDR-TB is a growing, complex, and costly problem that presents a major obstacle to TB control. Directly observed therapy (DOT) for treatment adherence monitoring is the recommended standard; however, it is challenging to implement at scale because it is labor-intensive. Mobile health interventions can facilitate remote adherence monitoring and minimize the costs and inconveniences associated with standard DOT.

Objective

The study aims to evaluate the effectiveness of using video directly observed therapy (VDOT) plus incentives to improve medication adherence in TB treatment versus usual-care DOT in an African context.

Methods

The DOT Selfie study is an open-label, randomized controlled trial (RCT) with 2 parallel groups, in which 144 adult patients with TB aged 18-65 years will be randomly assigned to receive the usual-care DOT monitoring or VDOT as the intervention. The intervention will consist of a smartphone app, a weekly internet subscription, translated text message reminders, and incentives for those who adhere. The participant will use a smartphone to record and send time-stamped encrypted videos showing their daily medication ingestion. This video component will directly substitute the need for daily face-to-face meetings between the health provider and patients. We hypothesize that the VDOT intervention will be more effective because it allows patients to swallow their pills anywhere, anytime. Moreover, patients will receive mobile-phone–based “social bundle” incentives to motivate adherence to continued daily submission of videos to the health system. The health providers will log into a secured computer system to verify treatment adherence, document missed doses, investigate the reasons for missed doses, and follow prespecified protocol measures to re-establish medication adherence. The primary endpoint is the adherence level as measured by the fraction of expected doses observed over the treatment period. The main secondary outcome will be time-to-treatment completion in both groups.

Results

This study was funded in 2019. Enrollment began in July and is expected to be completed by November 2020. Data collection and follow-up are expected to be completed by June 2021. Results from the analyses based on the primary endpoint are expected to be submitted for publication by December 2021.

Conclusions

This random control trial will be among the first to evaluate the effectiveness of VDOT within an African setting. The results will provide robust scientific evidence on the implementation and adoption of mobile health (mHealth) tools, coupled with incentives to motivate TB medication adherence. If successful, VDOT will apply to other low-income settings and a range of chronic diseases with lifelong treatment, such as HIV/AIDs.

Trial Registration

ClinicalTrials.gov NCT04134689; http://clinicaltrials.gov/ct2/show/NCT04134689

International Registered Report Identifier (IRRID)

DERR1-10.2196/18029

Excess Risk of Tuberculous Infection among Extra-Household Contacts of Tuberculosis Cases in an African City

RATIONALE

Although households of tuberculosis cases represent a setting for intense transmission of M. tuberculosis, household exposure accounts for less than 20% of transmission within a community.

OBJECTIVES

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 tuberculosis cases and matched controls without tuberculosis. We estimated the age-stratified prevalence difference of tuberculous 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 tuberculosis 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 tuberculosis 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.

Defining adequate contact for transmission of Mycobacterium tuberculosis in an African urban environment

Background

The risk of infection from respiratory pathogens increases according to the contact rate between the infectious case and susceptible contact, but the definition of adequate contact for transmission is not standard. In this study we aimed to identify factors that can explain the level of contact between tuberculosis cases and their social networks in an African urban environment.

Methods

This was a cross-sectional study conducted in Kampala, Uganda from 2013 to 2017. We carried out an exploratory factor analysis (EFA) in social network data from tuberculosis cases and their contacts. We evaluated the factorability of the data to EFA using the Kaiser-Meyer-Olkin Measure of Sampling Adequacy (KMO). We used principal axis factoring with oblique rotation to extract and rotate the factors, then we calculated factor scores for each using the weighted sum scores method. We assessed construct validity of the factors by associating the factors with other variables related to social mixing.

Results

Tuberculosis cases (N = 120) listed their encounters with 1154 members of their social networks. Two factors were identified, the first named “Setting” captured 61% of the variance whereas the second, named ‘Relationship’ captured 21%. Median scores for the setting and relationship factors were 10.2 (IQR 7.0, 13.6) and 7.7 (IQR 6.4, 10.1) respectively. Setting and Relationship scores varied according to the age, gender, and nature of the relationship among tuberculosis cases and their contacts. Family members had a higher median setting score (13.8, IQR 11.6, 15.7) than non-family members (7.2, IQR 6.2, 9.4). The median relationship score in family members (9.9, IQR 7.6, 11.5) was also higher than in non-family members (6.9, IQR 5.6, 8.1). For both factors, household contacts had higher scores than extra-household contacts (p < .0001). Contacts of male cases had a lower setting score as opposed to contacts of female cases. In contrast, contacts of male and female cases had similar relationship scores.

Conclusions

In this large cross-sectional study from an urban African setting, we identified two factors that can assess adequate contact between tuberculosis cases and their social network members. These findings also confirm the complexity and heterogeneity of social mixing.

Video directly observed therapy for supporting and monitoring adherence to tuberculosis treatment in Uganda: a pilot cohort study

Introduction

Nonadherence to treatment remains an obstacle to tuberculosis (TB) control worldwide. The aim of this study was to evaluate the feasibility of using video directly observed therapy (VDOT) for supporting TB treatment adherence in Uganda.

Methods

From May to December 2018, we conducted a pilot cohort study at a TB clinic in Kampala City. We enrolled patients aged 18–65 years with ≥3 months remaining of their TB treatment. Participants were trained to use a smartphone app to record videos of medication intake and submit them to a secured system. Trained health workers logged into the system to watch the submitted videos. The primary outcome was adherence measured as the fraction of expected doses observed (FEDO). In a secondary analysis, we examined differences in FEDO by sex, age, phone ownership, duration of follow-up, reasons for missed videos and patients' satisfaction at study exit.

Results

Of 52 patients enrolled, 50 were analysed. 28 (56%) were male, the mean age was 31 years (range 19–50 years) and 35 (70%) owned smartphones. Of the 5150 videos expected, 4231 (82.2%) were received. The median FEDO was 85% (interquartile range 66%–94%) and this significantly differed by follow-up duration. Phone malfunction, uncharged battery and VDOT app malfunctions were the commonest reasons for missed videos. 92% of patients reported being very satisfied with using VDOT.

Conclusion

VDOT was feasible and acceptable for monitoring and supporting TB treatment. It resulted in high levels of adherence, suggesting that digital technology holds promise in improving patient monitoring in Uganda.

Video directly observed therapy is feasible and acceptable for supporting and monitoring TB treatment adherence in a low-resource setting like Uganda. Digital health interventions hold promise as alternative methods for improving patient care.http://bit.ly/2Hxnvwu

There's no such thing as a free TB diagnosis: Catastrophic TB costs in Urban Uganda

Identifying and reducing TB-related costs is necessary for achieving the End TB Strategy's goal that no family is burdened with catastrophic costs. This study explores costs during the pre-diagnosis period and assesses the potential for using coping costs as a proxy indicator for catastrophic costs when comprehensive surveys are not feasible. Detailed interviews about TB-related costs and productivity losses were conducted with 196 pulmonary TB patients in Kampala, Uganda. The threshold for catastrophic costs was defined as 20% of household income. Multivariable regression analyses were used to assess the influence of patient characteristics on economic burden, and the positive predictive value (PPV) of coping costs was estimated. Over 40% of patients experienced catastrophic costs, with average (median) pre-diagnosis costs making up 30.6% (14.1%) of household income. Low-income status (AOR = 2.91, 95% CI = 1.29, 6.72), hospitalisation (AOR = 8.66, 95% CI = 2.60; 39.54), and coping costs (AOR = 3.84, 95% CI = 1.81; 8.40) were significantly associated with the experience of catastrophic costs. The PPV of coping costs as an indicator for catastrophic costs was estimated to be 73% (95% CI = 58%, 84%). TB patients endure a substantial economic burden during the pre-diagnosis period, and identifying households that experience coping costs may be a useful proxy measure for identifying catastrophic costs.

Performance of the QuantiFERON®-TB Gold In-Tube assay in tuberculin skin test converters: a prospective cohort study

OBJECTIVE

To investigate diagnostic agreement of the QuantiFERON®-TB Gold In-Tube (QFT-GIT) test in adult tuberculin skin test (TST) converters in a high tuberculosis (TB) burden setting.

SETTING AND DESIGN

We performed a case-cohort study from 2014 to 2016 in Uganda among residents who were not infected with Mycobacterium tuberculosis. Participants were followed up for 1 year, when they were retested to determine TST conversion. All TST converters and a random sample of participants from baseline were offered QFT-GIT testing.

RESULTS

Of 368 enrolled participants, 61 (17%) converted their TST by 1 year. Among 61 converters, 42 were tested using QFT-GIT, 64% of whom were QFT-GIT-positive. Of 307 participants with a persistent negative TST, 48 were tested using QFT-GIT, 83% of whom were QFT-negative. Overall concordance of TST and QFT-GIT was moderate (κ = 0.48, 95%CI 0.30-0.66). Converters with a conversion of 15 mm had a higher proportion of concordant QFT-GIT results (79%) than converters with increments of 10-14.9 mm (52%).

CONCLUSION

Concordance between TST and QFT-GIT was moderate among TST converters in this urban African population. These findings call for improved tests that more accurately measure conversion to tuberculous infection.

Screening tuberculosis patients for diabetes mellitus in a routine program setting in Kampala, Uganda: a cross-sectional study

Background: Uganda is located in East Africa and is among the countries with the lowest income globally. The ten health centres in this project serve populations in the under-privileged communities of Kampala. The objective of the study was to implement diabetes mellitus (DM) screening among tuberculosis (TB) patients in a routine program setting with limited resources and high human immunodeficiency virus (HIV) prevalence. Methods: A descriptive cross-sectional observational study was conducted in ten health centres in Kampala, Uganda. As part of a project to implement DM screening in a routine setting, TB patients were screened for DM by trained health workers. A fasting blood glucose (FBG) value ≥7.0mmol/l was considered to indicate DM. For this study, aggregate data was collected and analysed using SPSS for Windows, version 13.0. Results:  Among 4,590 TB patients registered, 4,016 (88.0%) were screened with random blood glucose (RBG). Of those with RBG ≥6.1mmol/l, 1,093 (83.3%) were screened with FBG. In total, 92 (2.3%) patients were diagnosed with DM and 66 (71.8%) of them were newly diagnosed. The proportion of TB patients screened with FBG in the health centres varied from 58.2% to 100%. The proportion of patients screened with FBG and the prevalence of DM were significantly higher in private health centres compared with public health centres. The health centres in peri-urban areas screened more patients with RBG than those in urban areas. Health centres without DM services screened a larger number of patients with RBG and FBG than those with DM services. Conclusions: It appears feasible to implement screening TB patients for DM in routine program settings with limited resources and high HIV prevalence. Its introduction requires close collaboration between TB and DM services. The challenges identified need government attention and certain institutional and service-related factors need to be better managed at times.

Screening tuberculosis patients for diabetes mellitus in a routine program setting in Kampala, Uganda: a cross-sectional study

Background: Uganda is located in East Africa and is among the countries with the lowest income globally. The ten health centres in this project serve populations in the under-privileged communities of Kampala. The objective of the study was to implement diabetes mellitus (DM) screening among tuberculosis (TB) patients in a routine program setting with limited resources and high human immunodeficiency virus (HIV) prevalence. Methods: A descriptive cross-sectional observational study was conducted in ten health centres in Kampala, Uganda. As part of a project to implement DM screening in a routine setting, TB patients were screened for DM by trained health workers. A fasting blood glucose (FBG) value ≥7.0mmol/l was considered to indicate DM. For this study, aggregate data was collected and analysed using SPSS for Windows, version 13.0. Results:  Among 4,590 TB patients registered, 4,016 (88.0%) were screened with random blood glucose (RBG). Of those with RBG ≥6.1mmol/l, 1,093 (83.3%) were screened with FBG. In total, 92 (2.3%) patients were diagnosed with DM and 66 (71.8%) of them were newly diagnosed. The proportion of TB patients screened with FBG in the health centres varied from 58.2% to 100%. The proportion of patients screened with FBG and the prevalence of DM were significantly higher in private health centres compared with public health centres. The health centres in peri-urban areas screened more patients with RBG than those in urban areas. These health centres without DM services screened a larger number of patients with RBG and FBG than those with DM services. Conclusions: It appears feasible to implement screening TB patients for DM in routine program settings with limited resources and high HIV prevalence. Its introduction requires close collaboration between TB and DM services. The challenges identified need government attention and certain institutional and service-related factors need to be better managed at times.

Serum n-6 Fatty Acids are Positively Associated with Growth in 6-to-10-Year Old Ugandan Children Regardless of HIV Status-A Cross-Sectional Study

Fatty acids (FAs) are crucial in child growth and development. In Uganda, antiretroviral therapy (ART) has drastically reduced perinatal human immunodeficiency virus (HIV) infection of infants, however, the interplay of FAs, ART, and HIV in relation to child growth is not well understood. To investigate this, serum was collected from 240 children between 6–10 years old in Uganda and analyzed for FAs using gas-chromatography mass-spectrometry. HIV status and anthropometric measurements were taken, and relationships with FAs were assessed. No significant differences in growth parameters or serum FAs were found between HIV uninfected children with and without exposure to ART. HIV positive children had significantly lower height-for-age-z-scores (HAZ) than uninfected children (p < 0.001). HIV-positive children had higher arachidonic acid than uninfected children (p = 0.003). Total omega-6 FAs were significantly associated with HAZ regardless of HIV status (p = 0.035). Mean total omega-3 FAs (2.90%) were low in this population compared to other cohorts in Africa. These results provide reference serum FA values for 6–10-year-old children in Uganda and may be used to inform lipid supplementation programs to promote child growth. Future studies should investigate the relationships between child growth trajectories in relation to HIV status and serum FAs.

Resistance and Susceptibility to Mycobacterium tuberculosis Infection and Disease in Tuberculosis Households in Kampala, Uganda

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a major public health problem. Household contact studies identify children and adults along the spectrum from Mtb exposure to disease. In the Kawempe Community Health Study (conducted in Kampala, Uganda), 872 culture-confirmed pulmonary TB cases and their 2,585 contacts were enrolled during 2002-2012 and followed for up to 2 years each. Risk factors identified by time-to-event analysis for secondary TB differed among children, women, and men. Younger age (P = 0.0061), human immunodeficiency virus (HIV) (P = 0.0002), thinness (P = 0.01), absent bacille Calmette-Guérin vaccination (P = 0.002), and epidemiologic risk score (P < 0.0001) were risks for children. For women, risks were HIV (P < 0.0001), thinness (World Health Organization criteria; P < 0.0001), and epidemiologic risk score (P = 0.003). For men, HIV (P = 0.0007) and low body mass index (P = 0.008) resulted in faster progression to TB. Tuberculin skin testing (TST) identified contacts with Mtb infection and those with persistently negative TST. Risks for faster time to Mtb infection were identified, and included age (P = 0.0007), baseline TST induration (P < 0.0001), and epidemiologic risk score (P < 0.0001) only in children. Those with persistently negative TST comprised 10% of contacts but had no unique epidemiologic characteristics among adults. The burden of Mtb infection and disease is high in TB households, and risk factors for progression from exposure to infection and disease differ among children, women, and men.

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.

Effectiveness of WHO's pragmatic screening algorithm for child contacts of tuberculosis cases in resource-constrained settings: a prospective cohort study in Uganda

BACKGROUND

Tuberculosis is a leading cause of global childhood mortality; however, interventions to detect undiagnosed tuberculosis in children are underused. Child contact tracing has been widely recommended but poorly implemented in resource-constrained settings. WHO has proposed a pragmatic screening approach for managing child contacts. We assessed the effectiveness of this screening approach and alternative symptom-based algorithms in identifying secondary tuberculosis in a prospectively followed cohort of Ugandan child contacts.

METHODS

We identified index patients aged at least 18 years with microbiologically confirmed pulmonary tuberculosis at Old Mulago Hospital (Kampala, Uganda) between Oct 1, 1995, and Dec 31, 2008. Households of index patients were visited by fieldworkers within 2 weeks of diagnosis. Coprevalent and incident tuberculosis were assessed in household contacts through clinical, radiographical, and microbiological examinations for 2 years. Disease rates were compared among children younger than 16 years with and without symptoms included in the WHO pragmatic guideline (presence of haemoptysis, fever, chronic cough, weight loss, night sweats, and poor appetite). Symptoms could be of any duration, except cough (>21 days) and fever (>14 days). A modified WHO decision-tree designed to detect high-risk asymptomatic child contacts was also assessed, in which all asymptomatic contacts were classified as high risk (children younger than 3 years or immunocompromised [HIV-infected]) or low risk (aged 3 years or older and immunocompetent [HIV-negative]). We also assessed a more restrictive algorithm (ie, assessing only children with presence of chronic cough and one other tuberculosis-related symptom).

FINDINGS

Of 1718 household child contacts, 126 (7%) had coprevalent tuberculosis and 24 (1%) developed incident tuberculosis, diagnosed over the 2-year study period. Of these 150 cases of tuberculosis, 95 (63%) were microbiologically confirmed with a positive sputum culture. Using the WHO approach, 364 (21%) of 1718 child contacts had at least one tuberculosis-related symptom and 85 (23%) were identified as having coprevalent tuberculosis, 67% of all coprevalent cases detected (diagnostic odds ratio 9·8, 95% CI 6·8-14·5; p<0·0001). 1354 (79%) of 1718 child contacts had no symptoms, of whom 41 (3%) had coprevalent tuberculosis. The WHO approach was effective in contacts younger than 5 years: 70 (33%) of 211 symptomatic contacts had coprevalent disease compared with 23 (6%) of 367 asymptomatic contacts (p<0·0001). This approach was also effective in contacts aged 5 years and older: 15 (10%) of 153 symptomatic contacts had coprevalent disease compared with 18 (2%) of 987 asymptomatic contacts (p<0·0001). More coprevalent disease was detected in child contacts recommended for screening when the study population was restricted by HIV-serostatus (11 [48%] of 23 symptomatic HIV-seropositive child contacts vs two [7%] of 31 asymptomatic HIV-seropositive child contacts) or to only culture-confirmed cases (47 [13%] culture confirmed cases of 364 symptomatic child contacts vs 29 [2%] culture confirmed cases of 1354 asymptomatic child contacts). In the modified algorithm, high-risk asymptomatic child contacts were at increased risk for coprevalent disease versus low-risk asymptomatic contacts (14 [6%] of 224 vs 27 [2%] of 1130; p=0·0021). The presence of tuberculosis infection did not predict incident disease in either symptomatic or asymptomatic child contacts: in symptomatic contacts, eight (5%) of 169 infected contacts and six (5%) of 111 uninfected contacts developed incident tuberculosis (p=0·80). Among asymptomatic contacts, incident tuberculosis occurred in six (<1%) of 795 contacts infected at baseline versus four (<1%) of 518 contacts uninfected at baseline, respectively (p=1·00).

INTERPRETATION

WHO's pragmatic, symptom-based algorithm was an effective case-finding tool, especially in children younger than 5 years. A modified decision-tree identified 6% of asymptomatic child contacts at high risk for subclinical disease. Increasing the feasibility of child-contact tracing using these approaches should be encouraged to decrease tuberculosis-related paediatric mortality in high-burden settings, but this should be partnered with increasing access to microbiological point-of-care testing.

FUNDING

National Institutes of Health, Tuberculosis Research Unit, AIDS International Training and Research Program of the Fogarty International Center, and the Center for AIDS Research.

Infectiousness of HIV-Seropositive Patients with Tuberculosis in a High-Burden African Setting

RATIONALE

Policy recommendations on contact investigation of HIV-seropositive patients with tuberculosis have changed several times. Current epidemiologic evidence informing these recommendations is considered low quality, and few large studies investigating the infectiousness of HIV-seropositive and -seronegative index cases have been performed in sub-Saharan Africa.

OBJECTIVES

We assessed the infectiousness of HIV-seropositive and -seronegative patients with tuberculosis to their household contacts and examined potential modifiers of this relationship.

METHODS

Adults suffering from their first episode of pulmonary tuberculosis were identified in Kampala, Uganda. Field workers visited index households and enrolled consenting household contacts. Latent tuberculosis infection was measured through tuberculin skin testing, and relative risks were calculated using modified Poisson regression models. Standard assessments of interaction between latent tuberculosis infection, the HIV serostatus of index cases, and other variables were performed.

MEASUREMENTS AND MAIN RESULTS

Latent tuberculosis infection was found in 577 of 878 (65.7%) and 717 of 974 (73.6%) household contacts of HIV-seropositive and -seronegative tuberculosis cases (relative risk, 0.89; 95% confidence interval, 0.82-0.97). On further stratification, cavitary lung disease (P < 0.0001 for interaction) and smear status (P = 0.02 for interaction) of tuberculosis cases modified the infectiousness of HIV-seropositive indexes. Cough duration of index cases did not display interaction (P = 0.499 for interaction).

CONCLUSIONS

This study suggests that HIV-seropositive tuberculosis cases may be less infectious than HIV-seronegative patients only when they are smear-negative or lack cavitary lung disease. These results may explain heterogeneity between prior studies and provide evidence suggesting that tuberculosis contact investigation should include HIV-seropositive index cases in high disease burden settings.

Tuberculosis case finding in first-degree relative contacts not living with index tuberculosis cases in Kampala, Uganda

PURPOSE

To assess the prevalence of pulmonary tuberculosis among first-degree relative (FDR) contacts not living with tuberculosis (TB) cases.

METHODS

A cross-sectional analysis of household contacts living with an index TB case and FDR contacts living outside of households in Kampala, Uganda, is presented.

RESULTS

A total of 177 contacts (52 FDRs and 125 index household contacts) of 31 TB cases were examined. Compared with index household contacts, FDR contacts were older, more likely to be TB symptomatic (50% vs 33%), had a higher percentage of abnormal chest X-rays (19% vs 11%), sputum smear positive (15% vs 5%), and many similar epidemiologic risk factors, including HIV infection (13% vs 10%). Contact groups had similar pulmonary tuberculosis prevalence: 9.6% in FDR vs 10.4% in index household contacts and similar Mycobacterium tuberculosis infection: 62% in FDR vs 61% in index households.

CONCLUSION

TB is common among FDR contacts. High TB prevalence justifies targeting FDRs during household contact investigations. Combining TB active-case finding among FDR contacts with household contact investigation in low-income setting is feasible. This should be part of national TB control program strategies for increasing TB case-detection rates and reducing community TB transmission and death.

Clinical and epidemiological characteristics of individuals resistant to M. tuberculosis infection in a longitudinal TB household contact study in Kampala, Uganda

Background

Despite sustained exposure to a person with pulmonary tuberculosis (TB), some M. tuberculosis (Mtb) exposed individuals maintain a negative tuberculin skin test (TST). Our objective was to characterize these persistently negative TST (PTST-) individuals and compare them to TST converters (TSTC) and individuals who are TST positive at study enrollment.

Methods

During a TB household contact study in Kampala, Uganda, PTST-, TSTC, and TST + individuals were identified. PTST- individuals maintained a negative TST over a 2 year observation period despite prolonged exposure to an infectious tuberculosis (TB) case. Epidemiological and clinical characteristics were compared, a risk score developed by another group to capture risk for Mtb infection was computed, and an ordinal regression was performed.

Results

When analyzed independently, epidemiological risk factors increased in prevalence from PTST- to TSTC to TST+. An ordinal regression model suggested age (p < 0.01), number of windows (p < 0.01) and people (p = 0.07) in the home, and sleeping in the same room (p < 0.01) were associated with PTST- and TSTC. As these factors do not exist in isolation, we examined a risk score, which reflects an accumulation of risk factors. This compound exposure score did not differ significantly between PTST-, TSTC, and TST+, except for the 5–15 age group (p = 0.009).

Conclusions

Though many individual factors differed across all three groups, an exposure risk score reflecting a collection of risk factors did not differ for PTST-, TSTC and TST + young children and adults. This is the first study to rigorously characterize the epidemiologic risk profile of individuals with persistently negative TSTs despite close exposure to a person with TB. Additional studies are needed to characterize possible epidemiologic and host factors associated with this phenotype.

Tuberculin skin test reversion following isoniazid preventive therapy reflects diversity of immune response to primary Mycobacterium tuberculosis infection

RATIONALE

Healthy household contacts (HHC) of individuals with Tuberculosis (TB) with Tuberculin Skin Test (TST) conversions are considered to harbor latent Mycobacterium tuberculosis (Mtb), and at risk for TB. The immunologic, clinical, and public health implications of TST reversions that occur following Isoniazid preventive therapy (IPT) remain controversial.

OBJECTIVES

To measure frequency of TST reversion following IPT, and variation in interferon-gamma (IFN-γ) responses to Mtb, in healthy Ugandan TB HHC with primary Mtb infection evidenced by TST conversion.

METHODS

Prospective cohort study of healthy, HIV-uninfected, TST-negative TB HHC with TST conversions. Repeat TST was performed 12 months following conversion (3 months following completion of 9 month IPT course) to assess for stable conversion vs. reversion. Whole blood IFN-γ responses to Mtb antigen 85B (MtbA85B) and whole Mtb bacilli (wMtb) were measured in a subset (n = 27 and n = 42, respectively) at enrollment and TST conversion, prior to initiation of IPT.

RESULTS

Of 122 subjects, TST reversion was noted in 25 (20.5%). There were no significant differences in demographic, clinical, or exposure variables between reverters and stable converters. At conversion, reverters had significantly smaller TST compared to stable converters (13.7 mm vs 16.4 mm, respectively; p = 0.003). At enrollment, there were no significant differences in IFN-γ responses to MtbA85B or wMTB between groups. At conversion, stable converters demonstrated significant increases in IFN-γ responses to Ag85B and wMtb compared to enrollment (p = 0.001, p<0.001, respectively), while there were no significant changes among reverters.

CONCLUSIONS

TST reversion following IPT is common following primary Mtb infection and associated with unique patterns of Mtb-induced IFN-γ production. We have demonstrated that immune responses to primary Mtb infection are heterogeneous, and submit that prospective longitudinal studies of cell mediated immune responses to Mtb infection be prioritized to identify immune phenotypes protective against development of TB disease.

Wasting among Uganda men with pulmonary tuberculosis is associated with linear regain in lean tissue mass during and after treatment in contrast to women with wasting who regain fat tissue mass: prospective cohort study

Background

Nutritional changes during and after tuberculosis treatment have not been well described. We therefore determined the effect of wasting on rate of mean change in lean tissue and fat mass as measured by bioelectrical impedance analysis (BIA), and mean change in body mass index (BMI) during and after tuberculosis treatment.

Methods

In a prospective cohort study of 717 adult patients, BMI and height-normalized indices of lean tissue (LMI) and fat mass (FMI) as measured by BIA were assessed at baseline, 3, 12, and 24 months.

Results

Men with wasting at baseline regained LMI at a greater rate than FMI (4.55 kg/m² (95% confidence interval (CI): 1.26, 7.83 versus 3.16 (95% CI: 0.80, 5.52)) per month, respectively during initial tuberculosis therapy. In contrast, women with wasting regained FMI at greater rate than LMI (3.55 kg/m² (95% CI: 0.40, 6.70) versus 2.07 (95% CI: -0.74, 4.88)), respectively. Men with wasting regained BMI at a rate of 6.45 kg/m² (95% CI: 3.02, 9.87) in the first three months whereas women, had a rate of 3.30 kg/m² (95% CI: -0.11, 6.72). There were minimal changes in body composition after month 3 and during months 12 to 24.

Conclusion

Wasted tuberculosis patients regain weight with treatment but the type of gain differs by gender and patients may remain underweight after the initial phase of treatment.

Contact investigation for active tuberculosis among child contacts in Uganda

BACKGROUND

Tuberculosis is a large source of morbidity and mortality among children. However, limited studies characterize childhood tuberculosis disease, and contact investigation is rarely implemented in high-burden settings. In one of the largest pediatric tuberculosis contact investigation studies in a resource-limited setting, we assessed the yield of contact tracing on childhood tuberculosis and indicators for disease progression in Uganda.

METHODS

Child contacts aged <15 years in Kampala, Uganda, were enrolled from July 2002 to June 2009 and evaluated for tuberculosis disease via clinical, radiographic, and laboratory methods for up to 24 months.

RESULTS

Seven hundred sixty-one child contacts were included in the analysis. Prevalence of tuberculosis in our child population was 10%, of which 71% were culture-confirmed positive. There were no cases of disseminated tuberculosis, and 483 of 490 children (99%) started on isoniazid preventative therapy did not develop disease. Multivariable testing suggested risk factors including human immunodeficiency virus (HIV) status (odds ratio [OR], 7.90; P < .001), and baseline positive tuberculin skin test (OR, 2.21; P = .03); BCG vaccination was particularly protective, especially among children aged ≤5 years (OR, 0.23; P < .001). Adult index characteristics such as sex, HIV status, and extent or severity of disease were not associated with childhood disease.

CONCLUSIONS

Contact tracing for children in high-burden settings is able to identify a large percentage of culture-confirmed positive tuberculosis cases before dissemination of disease, while suggesting factors for disease progression to identify who may benefit from targeted screening.

Genetic and shared environmental influences on interferon-γ production in response to Mycobacterium tuberculosis antigens in a Ugandan population

Interferon-γ (IFN-γ) is a key cytokine in the immune response to Mycobacterium tuberculosis (Mtb). Many studies established IFN-γ responses are influenced by host genetics, however differed widely by the study design and heritability estimation method. We estimated heritability of IFN-γ responses to Mtb culture filtrate (CF), ESAT-6, and Antigen 85B (Ag85B) in 1,104 Ugandans from a household contact study. Our method separately evaluates shared environmental and genetic variance, therefore heritability estimates were not upwardly biased, ranging from 11.6% for Ag85B to 22.9% for CF. Subset analyses of individuals with latent Mtb infection or without human immunodeficiency virus infection yielded higher heritability estimates, suggesting 10-30% of variation in IFN-γ is caused by a shared environment. Immunosuppression does not negate the role of genetics on IFN-γ response. These estimates are remarkably close to those reported for components of the innate immune response. These findings have implications for the interpretation of IFN-γ response assays and vaccine studies.

Lean tissue mass wasting is associated with increased risk of mortality among women with pulmonary tuberculosis in urban Uganda

OBJECTIVES

We assessed the impact of wasting on survival in patients with tuberculosis by using a precise height-normalized lean tissue mass index (LMI) estimated by bioelectrical impedance analysis and body mass index (BMI).

METHODS

In a retrospective cohort study, 747 adult pulmonary patients with tuberculosis who were screened for HIV and nutritional status were followed for survival.

RESULTS

Of 747 patients, 310 had baseline wasting by BMI (kg/m(2)) and 103 by LMI (kg/m(2)). Total deaths were 105. Among men with reduced BMI, risk of death was 70% greater (hazard ratio [HR] 1.7, 95% confidence interval [95% CI] 1.03-2.81) than in men with normal BMI. Survival did not differ by LMI among men (HR 1.1; 95% CI 0.5-2.9). In women, both the BMI and LMI were associated with survival. Among women with reduced BMI, risk of death was 80% greater (HR 1.8; 95% CI 0.9-3.5) than in women with normal BMI; risk of death was 5-fold greater (HR 5.0; 95% CI 1.6-15.9) for women with low LMI compared with women with normal LMI.

CONCLUSIONS

Wasting assessed by reduced BMI is associated with an increased risk for death among both men and women whereas reduced LMI is among women with tuberculosis.

Innate and adaptive immune responses during acute M. tuberculosis infection in adult household contacts in Kampala, Uganda

Contacts of active pulmonary tuberculosis (TB) patients are at risk for Mycobacterium tuberculosis (MTB) infection. Because most infections are controlled, studies during MTB infection provide insight into protective immunity. We compared immune responses of adult household contacts that did and did not convert the tuberculin skin test (TST). Innate and adaptive immune responses were measured by whole blood assay. Responses of TST converters (TSTC) were compared with persistently TST negative contacts (PTST-) and contacts who were TST+ at baseline (TST+). TLR-2, TLR-4, and IFN-γR responses to IFN-γ did not differ between the groups, nor did γδ T cell responses. T cell responses to MTB antigens differed markedly among TSTC, PTST-, and TST+ contacts. Thus, no differences in innate responses were found among the three household contact groups. However, adaptive T cell responses to MTB antigens did differ before and during MTB infection among PTST-, TSTC, and TST+ contacts.

CD8+ T cells provide an immunologic signature of tuberculosis in young children

RATIONALE

The immunologic events surrounding primary Mycobacterium tuberculosis infection and development of tuberculosis remain controversial. Young children who develop tuberculosis do so quickly after first exposure, thus permitting study of immune response to primary infection and disease. We hypothesized that M. tuberculosis-specific CD8(+) T cells are generated in response to high bacillary loads occurring during tuberculosis.

OBJECTIVES

To determine if M. tuberculosis-specific T cells are generated among healthy children exposed to M. tuberculosis and children with tuberculosis.

METHODS

Enzyme-linked immunosorbent spot assays were used to measure IFN-γ production in response to M. tuberculosis-specific proteins ESAT-6/CFP-10 by peripheral blood mononuclear cells and CD8(+) T cells isolated from Ugandan children hospitalized with tuberculosis (n = 96) or healthy tuberculosis contacts (n = 62).

MEASUREMENTS AND MAIN RESULTS

The proportion of positive CD8(+) T-cell assays and magnitude of CD8(+) T-cell responses were significantly greater among young (<5 yr) tuberculosis cases compared with young contacts (P = 0.02, Fisher exact test, P = 0.01, Wilcoxon rank-sum, respectively). M. tuberculosis-specific T-cell responses measured in peripheral blood mononuclear cells were equivalent between groups.

CONCLUSIONS

Among young children, M. tuberculosis-specific CD8(+) T cells develop in response to high bacillary loads, as occurs during tuberculosis, and are unlikely to be found after M. tuberculosis exposure. T-cell responses measured in peripheral blood mononuclear cells are generated after M. tuberculosis exposure alone, and thus cannot distinguish exposure from disease. In young children, IFN-γ-producing M. tuberculosis-specific CD8(+) T cells provide an immunologic signature of primary M. tuberculosis infection resulting in disease.

Genetic susceptibility to tuberculosis associated with cathepsin Z haplotype in a Ugandan household contact study

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), causes 9 million new cases worldwide and 2 million deaths annually. Genetic linkage and association analyses have suggested several chromosomal regions and candidate genes involved in TB susceptibility. This study examines the association of TB disease susceptibility with a selection of biologically relevant genes on regions on chromosomes 7 (IL6 and CARD11) and 20 (CTSZ and MC3R) and fine mapping of the chromosome 7p22-p21 region identified through our genome scan. We analyzed 565 individuals from Kampala, Uganda, who were previously included in our genome-wide linkage scan. Association analyses were conducted for 1,417 single-nucleotide polymorphisms (SNP) that passed quality control. None of the candidate gene or fine mapping SNPs was significantly associated with TB susceptibility (p > 0.10). When we restricted the analysis to HIV-negative individuals, 2 SNPs on chromosome 7 were significantly associated with TB susceptibility (p < 0.05). Haplotype analyses identified a significant risk haplotype in cathepsin X (CTSZ; p = 0.0281, odds ratio = 1.5493, 95% confidence interval [1.039, 2.320]).

Body composition among HIV-seropositive and HIV-seronegative adult patients with pulmonary tuberculosis in Uganda

PURPOSE

We determined whether human immunodeficiency virus (HIV) infection affects body cell mass and fat mass wasting among adults with pulmonary tuberculosis (PTB).

METHODS

We screened 967 Ugandan adults for PTB and HIV infection in a cross-sectional study. We compared anthropometric and bioelectric impedance analysis (BIA) body composition parameters among HIV-seropositive and HIV-seronegative men and women with or without PTB by using a non-parametric test.

RESULTS

We found that poor nutritional status associated with TB differed among men and women. Anthropometric and BIA body composition did not differ between HIV-seropositive and HIV-seronegative patients regardless of gender. Average weight group difference in men consisted of body cell mass and fat mass in equal proportions of 43%. In women, average weight group difference consisted predominantly of fat mass of 73% and body cell mass of 13%. Compared to individuals without TB, patients with TB had lower body mass index, weight, body cell mass, and fat mass regardless of gender and HIV status.

CONCLUSIONS

Gender, but not HIV status, was associated with body composition changes in TB. TB appears to be the dominant factor driving the wasting process among co-infected patients.

Genome scan of M. tuberculosis infection and disease in Ugandans

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is an enduring public health problem globally, particularly in sub-Saharan Africa. Several studies have suggested a role for host genetic susceptibility in increased risk for TB but results across studies have been equivocal. As part of a household contact study of Mtb infection and disease in Kampala, Uganda, we have taken a unique approach to the study of genetic susceptibility to TB, by studying three phenotypes. First, we analyzed culture confirmed TB disease compared to latent Mtb infection (LTBI) or lack of Mtb infection. Second, we analyzed resistance to Mtb infection in the face of continuous exposure, defined by a persistently negative tuberculin skin test (PTST-); this outcome was contrasted to LTBI. Third, we analyzed an intermediate phenotype, tumor necrosis factor-alpha (TNFα) expression in response to soluble Mtb ligands enriched with molecules secreted from Mtb (culture filtrate). We conducted a full microsatellite genome scan, using genotypes generated by the Center for Medical Genetics at Marshfield. Multipoint model-free linkage analysis was conducted using an extension of the Haseman-Elston regression model that includes half sibling pairs, and HIV status was included as a covariate in the model. The analysis included 803 individuals from 193 pedigrees, comprising 258 full sibling pairs and 175 half sibling pairs. Suggestive linkage (p<10⁻³) was observed on chromosomes 2q21-2q24 and 5p13-5q22 for PTST-, and on chromosome 7p22-7p21 for TB; these findings for PTST- are novel and the chromosome 7 region contains the IL6 gene. In addition, we replicated recent linkage findings on chromosome 20q13 for TB (p = 0.002). We also observed linkage at the nominal α = 0.05 threshold to a number of promising candidate genes, SLC11A1 (PTST- p = 0.02), IL-1 complex (TB p = 0.01), IL12BR2 (TNFα p = 0.006), IL12A (TB p = 0.02) and IFNGR2 (TNFα p = 0.002). These results confirm not only that genetic factors influence the interaction between humans and Mtb but more importantly that they differ according to the outcome of that interaction: exposure but no infection, infection without progression to disease, or progression of infection to disease. Many of the genetic factors for each of these stages are part of the innate immune system.

Whole blood interferon-gamma responses to mycobacterium tuberculosis antigens in young household contacts of persons with tuberculosis in Uganda

Background

Due to immunologic immaturity, IFN-γ-producing T cell responses may be decreased in young children compared to adults, thus we hypothesized that IFN-γ responses to mycobacterial antigens in household contacts exposed to Mycobacterium tuberculosis (Mtb) would be impaired in young children relative to adults. The objective of this study was to compare whole blood IFN-γ production in response to mycobacterial antigens between children and adults in Uganda.

Methodology/Principal Findings

We studied household contacts of persons with culture-positive pulmonary tuberculosis (TB) enrolled in a cohort study conducted in Kampala, Uganda. Whole blood IFN-γ production in response to Mtb culture-filtrate antigens was measured by ELISA and compared between infants (<2 years old, n = 80), young children (2 <5 years old, n = 216), older children (5 <15 years old, n = 443) and adults (≥15 years old, n = 528). We evaluated the relationship between IFN-γ responses and the tuberculin skin test (TST), and between IFN-γ responses and epidemiologic factors that reflect exposure to Mtb, and the effect of prior BCG vaccination on IFN-γ responses. Young household contacts demonstrated robust IFN-γ responses comparable to those of adults that were associated with TST and known risk factors for infection. There was no effect of prior BCG immunization on the IFN-γ response.

Conclusions/Significance

Young children in a TB endemic setting can mount robust IFN-γ responses generally comparable to those of adults, and as in adults, these responses correlated with the TST and known epidemiologic risk factors for Mtb infection.

Linkage and association analysis of candidate genes for TB and TNFalpha cytokine expression: evidence for association with IFNGR1, IL-10, and TNF receptor 1 genes

Tuberculosis (TB) is a growing public health threat globally and several studies suggest a role of host genetic susceptibility in increased TB risk. As part of a household contact study in Kampala, Uganda, we have taken a unique approach to the study of genetic susceptibility to TB by developing an intermediate phenotype model for TB susceptibility, analyzing levels of tumor necrosis factor-alpha (TNFalpha) in response to culture filtrate as the phenotype. In the present study, we analyzed candidate genes related to TNFalpha regulation and found that interleukin (IL)-10, interferon-gamma receptor 1 (IFNGR1), and TNFalpha receptor 1 (TNFR1) genes were linked and associated to both TB and TNFalpha. We also show that these associations are with progression to active disease and not susceptibility to latent infection. This is the first report of an association between TB and TNFR1 in a human population and our findings for IL-10 and IFNGR1 replicate previous findings. By observing pleiotropic effects on both phenotypes, we show construct validity of our intermediate phenotype model, which enables the characterization of the role of these genetic polymorphisms on TB pathogenesis. This study further illustrates the utility of such a model for disentangling complex traits.

Immune correlates of acute Mycobacterium tuberculosis infection in household contacts in Kampala, Uganda

To determine immunologic and epidemiologic correlates of acute Mycobacterium tuberculosis infection in household contacts of infectious tuberculosis cases, we performed a prospective, community-based cohort study of index cases and their household contacts in Kampala, Uganda. Contacts were evaluated for tuberculin skin test (TST) conversion over two years. Interferon-gamma expression was measured using a whole blood assay after stimulating with M. tuberculosis culture-filtrate. In 222 contacts with a TST less than 5 mm at baseline, the one-year rate of TST conversion was 27%. The TST conversion was associated with the infectiousness of the index case and proximity of contact. Interferon-gamma levels at baseline were greater among TST converters compared with those who did not convert. The risk of TST conversion increased four-fold as the baseline interferon-gamma increased 10-fold, but only in contacts with BCG vaccination. In household contacts of tuberculosis, interferon-gamma responses to non-specific mycobacterial antigens may be used to make an early diagnosis of tuberculosis infection, especially in resource-limited settings where bacille Calmette-Guérin vaccination is commonly used.

Vdelta2+ gammadelta T cell function in Mycobacterium tuberculosis- and HIV-1-positive patients in the United States and Uganda: application of a whole-blood assay

BACKGROUND

Vgamma9(+)Vdelta2(+) gammadelta T cells (Vdelta 2(+) T cells) are activated by Mycobacterium tuberculosis and secrete interferon (IFN)-gamma. Vdelta 2(+) T cells recognize phosphoantigens, such as bromohydrin pyrophosphate (BrHPP), and link innate and adaptive immunity.

METHODS

A whole-blood assay was developed that used IFN-gamma secretion in response to BrHPP as a measurement of Vdelta2(+) T cell function.

RESULTS

Peak IFN-gamma levels were detected after stimulating whole blood with BrHPP for 7-9 days. IFN- gamma production in whole blood in response to BrHPP paralleled IFN-gamma production and Vdelta2(+) T cell expansion of peripheral-blood mononuclear cells. The assay was used to evaluate Vdelta2(+) T cell function in subjects in the United States (n = 24) and Uganda (n = 178) who were or were not infected with M. tuberculosis and/or human immunodeficiency virus (HIV) type 1. When 50 micromol/L BrHPP was used, 100% of healthy subjects produced IFN-gamma. The Vdelta2(+) T cell response was independent of the tuberculin skin test response. In Uganda, Vdelta2(+) T cell responses were decreased in patients with tuberculosis (n = 73) compared with responses in household contacts (n = 105). HIV-1-positive household contacts had lower responses than did HIV-1-negative household contacts. HIV-1-positive patients with tuberculosis had the lowest V delta 2(+) T cell responses.

CONCLUSIONS

Tuberculosis and HIV-1 infection are associated with decreased Velta2(+) T cell function. Decreased Vdelta2(+) T cell function may contribute to increased risk for tuberculosis in HIV-1-positive patients.

Burden of tuberculosis in Kampala, Uganda

OBJECTIVE

To determine the prevalence and incidence of tuberculosis in one of Uganda's poor peri-urban areas.

METHODS

Multi-stage sampling was used to select a sample of households whose members were evaluated for presence of signs and/or symptoms of active tuberculosis; history of tuberculosis treatment; and relevant demographic, socioeconomic, and household environment characteristics. Patients with suspected tuberculosis underwent standardized evaluation for active disease.

FINDINGS

A sample of 263 households with 1142 individuals was evaluated. Nineteen people were classified as having had tuberculosis during the one-year reference period (May 2001-April 2002): nine (47%) cases already had been diagnosed through the health care system, while 10 cases (53%) were diagnosed through the survey. The prevalences for all forms of tuberculosis and for sputum smear-positive tuberculosis were 14.0 (95% confidence interval (CI) 7.8-20.3) and 4.4 (CI = 0.83-7.89) per thousand, respectively. The incidences for all forms of tuberculosis and for sputum smear-positive tuberculosis were 9.2 (CI = 3.97-14.4) and 3.7 (CI = 0.39-6.95) per thousand per year, respectively.

CONCLUSION

The rate of tuberculosis in this peri-urban community was exceptionally high and may be underestimated by current surveillance systems. The need for interventions aimed at reducing tuberculosis transmission in this, and other similar communities with high case rates, is urgent.