New Measurable Indicator for Tuberculosis Case Detection

Conducting prevalence surveys at 5- to 10-year intervals would allow countries to determine their case detection performance

Evaluating Tuberculosis Case Detection in Eritrea

We used results from a national tuberculosis prevalence survey in Eritrea to calculate case detection rate (CDR) and compared it with the published CDR. The CDR obtained from the survey was ≈40%, whereas the CDR published by the World Health Organization was 3× lower (14%)

What is the true tuberculosis mortality burden? Differences in estimates by the World Health Organization and the Global Burden of Disease study

Background: The World Health Organization (WHO) and the Global Burden of Disease (GBD) study at the Institute for Health Metrics and Evaluation (IHME) periodically provide global estimates of tuberculosis (TB) mortality. We compared the 2015 WHO and GBD TB mortality estimates and explored which factors might drive the differences. Methods: We extracted the number of estimated TB-attributable deaths, disaggregated by age, HIV status, sex and country from publicly available WHO and GBD datasets for the year 2015. We ‘standardized’ differences between sources by adjusting each country’s difference in absolute number of deaths by the average number of deaths estimated by both sources. Results: For 195 countries with estimates from both institutions, WHO estimated 1 768 482 deaths attributable to TB, whereas GBD estimated 1 322 916 deaths, a difference of 445 566 deaths or 29% of the average of the two estimates. The countries with the largest absolute differences in deaths were Nigeria (216 621), Bangladesh (49 863) and Tanzania (38 272). The standardized difference was not associated with HIV prevalence, prevalence of multidrug resistance or global region, but did show correlation with the case detection rate as estimated by WHO [r ¼ 0.37, 95% confidence interval (CI): 049; 0.24] or, inversely, with case detection rate based on GBD data (r ¼ 0.44, 95% CI: 0.31; 0.54). Countries with a recent national prevalence survey had higher standardized differences (higher estimates by WHO) than those without (P ¼ 0.006). After exclusion of countries with recent prevalence surveys, the overall correlation between both estimates was r ¼ 0.991. Conclusions: A few countries account for the large global discrepancy in TB mortality estimates. The differences are due to the methodological approaches used by WHO and GBD. The use and interpretation of prevalence survey data and case detection rates seem to play a role in the observed differences

Extrapulmonary Tuberculosis by Nationality, the Netherlands, 1993–2001

The growth of the number of inhabitants with a non-Western ethnic background most likely explains the growth of extrapulmonary TB in the Netherlands

The incidence of tuberculosis among hiv-positive individuals with high CD4 counts: implications for policy

Intensified case finding (ICF) and earlier antiretroviral therapy (ART) initiation are strategies to reduce burden of HIV-associated tuberculosis (TB). We describe incidence of and associated factors for TB among HIV-positive individuals with CD4 counts > 350 cells/μl in South Africa. Prospective cohort study of individuals recruited for a TB vaccine trial. Eligible individuals without prevalent TB were followed up at 6 and 12 months after enrolment. Cox proportional hazards regression was used to determine factors associated with risk of incident TB. Six hundred thirty-four individuals were included in the analysis [80.9 % female, 57.9 % on ART, median CD4 count 562 cells/μl (IQR 466-694 cells/μl)]. TB incidence was 2.7 per 100 person-years (pyrs) (95 % CI 1.6-4.4 per 100 pyrs) and did not differ significantly between those on ART and those not on ART [HR 0.65 (95 % CI 0.24-1.81)]. Low body mass index (BMI <18.5 kg/m(2)) was associated with incident TB [HR 3.87 (95 % CI 1.09-13.73)]. Half of the cases occurred in the first 6 months of follow up and may have been prevalent or incubating cases at enrolment. TB incidence was high and associated with low BMI. Intensified case finding for TB should be strengthened for all HIV positive individuals regardless of their CD4 count or ART statu

Transmission and progression to disease of Mycobacterium tuberculosis phylogenetic lineages in The Netherlands

The aim of this study was to determine if mycobacterial lineages affect infection risk, clustering, and disease progression among Mycobacterium tuberculosis cases in The Netherlands. Multivariate negative binomial regression models adjusted for patient-related factors and stratified by patient ethnicity were used to determine the association between phylogenetic lineages and infectivity (mean number of positive contacts around each patient) and clustering (as defined by number of secondary cases within 2 years after diagnosis of an index case sharing the same fingerprint) indices. An estimate of progression to disease by each risk factor was calculated as a bootstrapped risk ratio of the clustering index by the infectivity index. Compared to the Euro-American reference, Mycobacterium africanum showed significantly lower infectivity and clustering indices in the foreign-born population, while Mycobacterium bovis showed significantly lower infectivity and clustering indices in the native population. Significantly lower infectivity was also observed for the East African Indian lineage in the foreign-born population. Smear positivity was a significant risk factor for increased infectivity and increased clustering. Estimates of progression to disease were significantly associated with age, sputum-smear status, and behavioral risk factors, such as alcohol and intravenous drug abuse, but not with phylogenetic lineages. In conclusion, we found evidence of a bacteriological factor influencing indicators of a strain's transmissibility, namely, a decreased ability to infect and a lower clustering index in ancient phylogenetic lineages compared to their modern counterparts. Confirmation of these findings via follow-up studies using tuberculin skin test conversion data should have important implications on M. tuberculosis control efforts.This study was supported by the Portuguese Foundation for Science and Technology (FCT) (reference SFRH/BD/33902/2009 to H.N.-G

A Tuberculin Skin Test Survey and the Annual Risk of Mycobacterium tuberculosis Infection in Gambian School Children.

BACKGROUND: A Tuberculin skin test (TST) survey was conducted to assess the prevalence of latent TB Infection (LTBI) and to estimate the annual risk of M. tuberculosis infection (ARTI) in Gambian school children. The results are expected to contribute to understanding of Tuberculosis epidemiology in The Gambia. METHODS: This was a nationwide, multi-cluster survey in children aged 6-11 years. Districts, 20 of 37, were selected by probability proportional to size and schools by simple random sampling. All TST were performed using the Mantoux method. Height and weight measurements were obtained for all participants. We calculated prevalence of LTBI using cut-off points of 10mm, the mirror and mixture modelling methods. RESULTS: TST readings were completed 13,386 children with median age of 9 years (interquartile range [IQR] 8-10 years). Mixture analysis yielded a cut-off point of 12 mm, and LTBI prevalence of 6.9% [95%CI 6.47-7.37] and the ARTI was 0.75% [95%CI 0.60-0.91]. LTBI was associated gender and urban residence (p <0.01). Nutritional status was not associated with non-reactive TST or sizes of TST indurations. ARTI did not differ significantly by age, gender, BCG vaccination or residence. CONCLUSIONS: This estimates for LTBI prevalence and ARTI were low but this survey provides updated data. Malnutrition did not affect estimates of LTBI and ARTI. Given the low ARTI in this survey and the overlapping distribution of indurations with mixture modelling, further surveys may require complementary tests such as interferon gamma release assays or novel diagnostic tools

High Incidence of Pulmonary Tuberculosis a Decade after Immigration, Netherlands

Incidence rates of pulmonary tuberculosis among immigrants from high incidence countries remain high for at least a decade after immigration into the Netherlands. Possible explanations are reactivation of old infections and infection transmitted after immigration. Control policies should be determined on the basis of the as-yet unknown main causes of the persistent high incidence

Drivers of Tuberculosis Transmission.

Measuring tuberculosis transmission is exceedingly difficult, given the remarkable variability in the timing of clinical disease after Mycobacterium tuberculosis infection; incident disease can result from either a recent (ie, weeks to months) or a remote (ie, several years to decades) infection event. Although we cannot identify with certainty the timing and location of tuberculosis transmission for individuals, approaches for estimating the individual probability of recent transmission and for estimating the fraction of tuberculosis cases due to recent transmission in populations have been developed. Data used to estimate the probable burden of recent transmission include tuberculosis case notifications in young children and trends in tuberculin skin test and interferon γ-release assays. More recently, M. tuberculosis whole-genome sequencing has been used to estimate population levels of recent transmission, identify the distribution of specific strains within communities, and decipher chains of transmission among culture-positive tuberculosis cases. The factors that drive the transmission of tuberculosis in communities depend on the burden of prevalent tuberculosis; the ways in which individuals live, work, and interact (eg, congregate settings); and the capacity of healthcare and public health systems to identify and effectively treat individuals with infectious forms of tuberculosis. Here we provide an overview of these factors, describe tools for measurement of ongoing transmission, and highlight knowledge gaps that must be addressed