Refining the definition of miliary/disseminated tuberculosis in Canada.

Objectives: Although a "multisite" definition of disseminated tuberculosis (DTB) exists, there is limited evidence to support its use. Herein, we sought to generate that evidence.

Methods: We evaluated treatment outcomes and reporting requirements against two distinct definitions of DTB in a 15-year population-based cohort of consecutively diagnosed patients with tuberculosis (TB) in Canada.

The association between phylogenetic lineage and the subclinical phenotype of pulmonary tuberculosis: A retrospective 2-cohort study.

Background: Subclinical pulmonary tuberculosis (PTB) is an asymptomatic disease state between established TB infection and symptomatic (clinical) TB disease. It is present in 20-25% of PTB patients in high-income countries. Mycobacterium tuberculosis complex (MTBC) genetic heterogeneity, and differential host immunological responses, have been implicated in its pathogenesis.

Limitations of Chest Radiography in Diagnosing Subclinical Pulmonary Tuberculosis in Canada.

Subclinical pulmonary tuberculosis (PTB) is defined as "…a state of disease due to viable that does not cause TB-related symptoms but does cause other abnormalities that can be detected using existing radiologic and mycobacteriologic assays." In high-income countries, subclinical PTB is usually diagnosed during active case finding, is acid-fast bacilli smear negative, and associated with minimal or no lung parenchymal abnormality on chest radiograph. In the absence of symptoms, the epidemiologic risk of TB and chest radiograph are critical to making the diagnosis.

The prevalence, risk factors, and public health consequences of peripheral lymph node-associated clinical and subclinical pulmonary tuberculosis.

Objectives: Relatively little is known about the prevalence, risk factors, and public health consequences of peripheral lymph node (PLN)-associated pulmonary tuberculosis (PTB).

Methods: We developed a 10-year (2010-2019) population-based cohort of PLNTB patients in Canada. We used systematically collected primary source data and expert reader chest radiograph interpretations in a multivariable logistic regression to determine associations between sputum culture positivity and demographic, clinical, and radiographic features.

A comparison of the chest radiographic and computed tomographic features of subclinical pulmonary tuberculosis.

Subclinical pulmonary tuberculosis (PTB) is a recently described intermediate state of great interest, but about which little is known. This study sought to describe and compare the frequency of key radiologic features of subclinical PTB on chest radiograph (CXR) versus computed tomographic scan (CT), and to interpret the clinical and public health relevance of the differences. Diagnostic CXRs and CT scans of the thorax and neck in a 16-year cohort of subclinical PTB patients in Canada were re-acquired and read by two independent readers and arbitrated by a third reader.

The Radiographic and Mycobacteriologic Correlates of Subclinical Pulmonary TB in Canada: A Retrospective Cohort Study.

Background: Very little is known about subclinical pulmonary TB (PTB), a recently described intermediate state, in high-income countries.

Research Question: What is the prevalence of subclinical PTB in Canada? What are its diagnostic chest radiography features? What is the relationship between those features and time to culture positivity, and what is the association between DNA fingerprint clustering, a measure of local transmission, and radiographic or other features in the foreign-born?

Study Design And Methods: We used primary source data to identify a 16-year retrospective cohort of patients with PTB. Demographic and mycobacteriologic features in patients with subclinical and clinical disease were compared, and the reason for assessment of patients with subclinical disease was described.

How much do smear-negative patients really contribute to tuberculosis transmissions? Re-examining an old question with new tools.

Background: Sputum smear microscopy is a common surrogate for tuberculosis infectiousness. Previous estimates that smear-negative patients contribute 13-20% of transmissions and are, on average, 20 to 25% as infectious as smear-positive cases are understood to be high. Herein, we use an ideal real-world setting, a comprehensive dataset, and new high-resolution techniques to more accurately estimate the true transmission risk of smear-negative cases.

Individual and public health consequences associated with a missed diagnosis of pulmonary tuberculosis in the emergency department: A retrospective cohort study.

Objectives: To determine: i) the emergency department (ED) utilization history of pulmonary tuberculosis (PTB) patients, and ii) the potential individual and public health consequences of a missed diagnosis of PTB in this setting.

Design: Retrospective observational cohort study.

Participants: Patients with PTB aged >16 years diagnosed between April 1, 2010 and December 31, 2016 in the Province of Alberta, Canada.

Local Transmission Plays No Important Role in the Occurrence of Multidrug-Resistant Tuberculosis in Immigrants to Canada: An In-depth Epidemiologic Analysis.

Background: Multidrug-resistant (MDR) tuberculosis has increased among migrants in Canada. The cause(s) of this increase is unknown.

Methods: We performed a retrospective cohort study in a Canadian province with substantially increased immigration between 1982-2001 and 2002-2019.

Prompt recognition of infectious pulmonary tuberculosis is critical to achieving elimination goals: a retrospective cohort study.

Introduction: All pulmonary tuberculosis (PTB) cases are presumed to be infectious to some degree. This spectrum of infectiousness is independently described by both the acid-fast bacilli smear and radiographic findings. Smear-positive patients with chest radiographic findings that are typical for adult-type PTB are believed to be most infectious.

Is there a fundamental flaw in Canada's post-arrival immigrant surveillance system for tuberculosis?

Background: New immigrants to Canada with a history of tuberculosis or evidence of old healed tuberculosis on chest radiograph are referred to public health authorities for medical surveillance. This ostensible public health protection measure identifies a subgroup of patients (referrals) who are at very low risk (compared to non-referrals) of transmission.

Methods: To assess whether earlier diagnosis or a different phenotypic expression of disease explains this difference, we systematically reconstructed the immigration and transmission histories from a well-defined cohort of recently-arrived referral and non-referral pulmonary tuberculosis cases in Canada.

Epidemiological and genomic determinants of tuberculosis outbreaks in First Nations communities in Canada.

Background: In Canada, tuberculosis disproportionately affects foreign-born and First Nations populations. Within First Nations' peoples, a high proportion of cases occur in association with outbreaks. Tuberculosis transmission in the context of outbreaks is thought to result from the convergence of several factors including characteristics of the cases, contacts, the environment, and the pathogen.

Predicting pulmonary tuberculosis in immigrants: a retrospective cohort study.

Our objective was to investigate whether pulmonary tuberculosis (PTB) can be predicted from features of a targeted medical history and basic laboratory investigations in immigrants. A retrospective cohort of 391 foreign-born adults referred to the Edmonton Tuberculosis Clinic (Edmonton, AB, Canada) was studied using multiple logistic regression analysis to predict PTB. Seven characteristics of disease were used as explanatory variables.

Do "Virtual" and "Outpatient" Public Health Tuberculosis Clinics Perform Equally Well? A Program-Wide Evaluation in Alberta, Canada.

Background: Meeting the challenge of tuberculosis (TB) elimination will require adopting new models of delivering patient-centered care customized to diverse settings and contexts. In areas of low incidence with cases spread out across jurisdictions and large geographic areas, a "virtual" model is attractive. However, whether "virtual" clinics and telemedicine deliver the same outcomes as face-to-face encounters in general and within the sphere of public health in particular, is unknown.

Is early tuberculosis death associated with increased tuberculosis transmission?

Introduction: Tuberculosis (TB) is now a relatively uncommon disease in high income countries. As such, its diagnosis may be missed or delayed resulting in death before or shortly after the introduction of treatment. Whether early TB death is associated with increased TB transmission is unknown.

A 10-year population based study of 'opt-out' HIV testing of tuberculosis patients in Alberta, Canada: national implications.

Introduction: Compliance with the recommendation that all tuberculosis (TB) patients be tested for human immunodeficiency virus (HIV) has not yet been achieved in Canada or globally.

Methods: The experience of "opt-out" HIV testing of TB patients in the Province of Alberta, Canada is described over a 10-year period, 2003-2012. Testing rates are reported before and after the introduction of the "opt-out" approach.