International research and guidelines on post-tuberculosis chronic lung disorders: a systematic scoping review

Post-tuberculosis airway disease: A population-based cohort study of people immigrating to British Columbia, Canada, 1985-2015

BACKGROUND

Current epidemiological evidence of post-TB airway disease is largely cross-sectional and derived from high-TB-incidence settings. We present the first cohort study of post-TB airway disease in a low-TB-incidence setting.

AIMS

(1) analyze the risk of airway disease by respiratory TB, (2) assess potential unmeasured confounding between TB and airway disease, and (3) investigate TB effect measure modification.

METHODS

A population-based cohort study using healthcare claims data for immigrants to British Columbia (BC), Canada, 1985-2015. Airway disease included chronic airway obstruction, asthma, bronchitis, bronchiolitis, and emphysema. Respiratory TB was defined from TB registry data. Cox proportional hazards (PH) regressions were used to analyze time-to-airway disease by respiratory TB. Sensitivity analyses included varying definitions of TB and airway disease. Potential unmeasured confounding by smoking was evaluated by E-value and hybrid least absolute shrinkage and selection operator (LASSO)-high-dimensional propensity score (hdPS).

FINDINGS

In our cohort (N = 1 005 328; n_TB=1141) there were 116 840 incident cases of airway disease during our 30-year study period (10.43 per 1,000 person-years of follow-up), with cumulative incidence of 42·5% among respiratory TB patients compared with 11·6% among non-TB controls. The covariate-adjusted hazard ratio (aHR) for airway disease by respiratory TB was 2·08 (95% CI: 1·91-2·28) with E-value=3·58. The LASSO-hdPS analysis produced aHR=2·26 (95% CI: 2·07-2·47).

INTERPRETATION

A twofold higher risk of airway disease was observed among immigrants diagnosed with respiratory TB, compared with non-TB controls, in a low-TB-incidence setting. Unmeasured confounding is unlikely to explain this relationship. Models of post-TB care are needed.

FUNDING

Canadian Institutes of Health Research.

Small Airways Disease, Biomarkers and COPD: Where are We?

The response to treatment and progression of Chronic Obstructive Pulmonary Disease (COPD) varies significantly. Small airways disease (SAD) is being increasingly recognized as a key pathological feature of COPD. Studies have brought forward pathological evidence of small airway damage preceding the development of emphysema and the detection of obstruction using traditional spirometry. In recent years, there has been a renewed interest in the early detection of SAD and this has brought along an increased demand for physiological tests able to identify and quantify SAD. Early detection of SAD allows early targeted therapy and this suggests the potential for altering the course of disease. The aim of this article is to review the evidence available on the physiological testing of small airways. The first half will focus on the role of lung function tests such as maximum mid-expiratory flow, impulse oscillometry and lung clearance index in detecting and quantifying SAD. The role of Computed Tomography (CT) as a radiological biomarker will be discussed as well as the potential of recent CT analysis software to differentiate normal aging of the lungs to pathology. The evidence behind SAD biomarkers sourced from blood as well as biomarkers sourced from sputum and broncho-alveolar lavage (BAL) will be reviewed. This paper focuses on CC-16, sRAGE, PAI-1, MMP-9 and MMP-12.

Post-tuberculosis mortality risk among immigrants to British Columbia, Canada, 1985-2015: a time-dependent Cox regression analysis of linked immigration, public health, and vital statistics data

OBJECTIVE

To compare non-tuberculosis (non-TB)-cause mortality risk overall and cause-specific mortality risks within the immigrant population of British Columbia (BC) with and without TB diagnosis through time-dependent Cox regressions.

METHODS

All people immigrating to BC during 1985-2015 (N = 1,030,873) were included with n = 2435 TB patients, and the remaining as non-TB controls. Outcomes were time-to-mortality for all non-TB causes, respiratory diseases, cardiovascular diseases, cancers, and injuries/poisonings, and were ascertained using ICD-coded vital statistics data. Cox regressions were used, with a time-varying exposure variable for TB diagnosis.

RESULTS

The non-TB-cause mortality hazard ratio (HR) was 4.01 (95% CI 3.57-4.51) with covariate-adjusted HR of 1.69 (95% CI 1.50-1.91). Cause-specific covariate-adjusted mortality risk was elevated for respiratory diseases (aHR = 2.96; 95% CI 2.18-4.00), cardiovascular diseases (aHR = 1.63; 95% CI 1.32-2.02), cancers (aHR = 1.40; 95% CI 1.13-1.75), and injuries/poisonings (aHR = 1.85; 95% CI 1.25-2.72).

CONCLUSIONS

In any given year, if an immigrant to BC was diagnosed with TB, their risk of non-TB mortality was 69% higher than if they were not diagnosed with TB. Healthcare providers should consider multiple potential threats to the long-term health of TB patients during and after TB treatment. TB guidelines in high-income settings should address TB survivor health.

Post-Tuberculosis Lung Disease: Clinical Review of an Under-Recognised Global Challenge

An estimated 58 million people have survived tuberculosis since 2000, yet many of them will suffer from post-tuberculosis lung disease (PTLD). PTLD results from a complex interplay between organism, host, and environmental factors and affects long-term respiratory health. PTLD is an overlapping spectrum of disorders that affects large and small airways (bronchiectasis and obstructive lung disease), lung parenchyma, pulmonary vasculature, and pleura and may be complicated by co-infection and haemoptysis. People affected by PTLD have shortened life expectancy and increased risk of recurrent tuberculosis, but predictors of long-term outcomes are not known. No data are available on PTLD in children and on impact throughout the life course. Risk-factors for PTLD include multiple episodes of tuberculosis, drug-resistant tuberculosis, delays in diagnosis, and possibly smoking. Due to a lack of controlled trials in this population, no evidence-based recommendations for the investigation and management of PTLD are currently available. Empirical expert opinion advocates pulmonary rehabilitation, smoking cessation, and vaccinations (pneumococcal and influenza). Exacerbations in PTLD remain both poorly understood and under-recognised. Among people with PTLD, the probability of tuberculosis recurrence must be balanced against other causes of symptom worsening. Unnecessary courses of repeated empiric anti-tuberculosis chemotherapy should be avoided. PTLD is an important contributor to the global burden of chronic lung disease. Advocacy is needed to increase recognition for PTLD and its associated economic, social, and psychological consequences and to better understand how PTLD sequelae could be mitigated. Research is urgently needed to inform policy to guide clinical decision-making and preventative strategies for PTLD.

Chronic Pulmonary Aspergillosis in Post Tuberculosis Patients in Indonesia and the Role of LDBio Aspergillus ICT as Part of the Diagnosis Scheme

Chronic pulmonary aspergillosis (CPA) is a common sequela of pulmonary tuberculosis (TB). The diagnosis of CPA is difficult and often misdiagnosed as smear-negative TB in endemic settings. Aspergillus IgG detection is the cornerstone of CPA diagnosis. There are a lack of studies on the prevalence of CPA in GeneXpert/smear-negative TB patients in Indonesia, despite a high number of TB cases. This study aims to determine the CPA rate in HIV-negative, GeneXpert-negative patients presenting with symptoms following completion of TB therapy and to evaluate the performance of LDBio Aspergillus immunochromatographic technology (ICT) lateral flow assay in the diagnosis of CPA. CPA was diagnosed on the basis of symptoms for ≥3 months, characteristic chest imaging and positive Aspergillus culture. Twenty (22%) out of 90 patients met the criteria for CPA. The LDBio test was positive in 16 (80%) CPA patients and in 21 (30%) non-CPA patients (p < 0.001) with 80% sensitivity and 70% specificity. Logistic regression revealed a positive LDBio Aspergillus ICT result, smoking history and diabetes to be important predictors of CPA diagnosis. Although CPA is an unrecognised disease in Indonesia, this study suggests that more than one in five GeneXpert negative patients with persistent symptoms following completion of TB therapy may have CPA.

Neutrophils in Tuberculosis-Associated Inflammation and Lung Pathology

Protective immunity to Mycobacterium tuberculosis (Mtb)—the causative agent of tuberculosis (TB)—is not fully understood but involves immune responses within the pulmonary airways which can lead to exacerbated inflammation and immune pathology. In humans, this inflammation results in lung damage; the extent of which depends on specific host pro-inflammatory processes. Neutrophils, though increasingly linked to the development of inflammatory disorders, have been less well studied in relation to TB-induced lung pathology. Neutrophils mode of action and their specialized functions can be directly linked to TB-specific lung tissue damage observed on patient chest X-rays at diagnosis and contribute to long-term pulmonary sequelae. This review discusses aspects of neutrophil activity associated with active TB, including the resulting inflammation and pulmonary impairment. It highlights the significance of neutrophil function on TB disease outcome and underlines the necessity of monitoring neutrophil function for better assessment of the immune response and severity of lung pathology associated with TB. Finally, we propose that some MMPs, ROS, MPO, S100A8/A9 and Glutathione are neutrophil-related inflammatory mediators with promising potential as targets for developing host-directed therapies for TB.

Obstructive lung disease and quality of life after cure of multi-drug-resistant tuberculosis in Uganda: a cross-sectional study

Background

Pulmonary multi-drug-resistant tuberculosis (MDR TB) alters lung architecture and involves lengthy treatment duration, high pill burden, drug adverse effects, travel restrictions, and stigma. Literature about pulmonary function and health-related quality of life (QoL) of patients treated for MDR TB is limited. This study sought to determine the prevalence of chronic obstructive pulmonary disease (COPD) and QoL of patients who were treated for pulmonary MDR TB.

Methods

Participants who completed 18 months of pulmonary MDR TB treatment and considered cured were eligible to be evaluated in a cross-sectional study. We performed post-bronchodilator spirometry to measure forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC). COPD was defined as FEV₁/FVC < 0.7; health-related QoL was assessed using the Medical Outcomes Survey for HIV (MOS-HIV) and St. George's Respiratory Questionnaire (SGRQ). Linear and logistic regression models were used to assess associations with COPD, health-related QoL, and other characteristics of the cohort.

Results

A total of 95 participants were enrolled. Median age of the cohort was 39 years (interquartile range (IQR), 29-45), and 55 (58%) were HIV-positive. COPD prevalence was 23% (22/95). Median SGRQ score was normal at 7.8 (IQR, 3.1-14.8). Median mental and physical health summary scores were significantly impaired, at 58.6 (IQR, 52.0-61.5) and 52.9 (IQR, 47.8-57.9), respectively, on a scale of 0 to 100 where 100 represents excellent physical or mental health. In this sample, 19% (18/95) of participants were in the lowest relative socioeconomic position (SEP) while 34% (32/95) were in the highest relative SEP. Belonging in the lowest SEP group was the strongest predictor of COPD.

Conclusion

Individuals who have completed MDR TB treatment have a high prevalence of COPD and low mental and physical health summary scores. Our study highlights the need for pulmonary rehabilitation programs in patients with a low socioeconomic position (SEP) after MDR TB treatment.

Development of chronic lung impairment in Mozambican TB patients and associated risks

BACKGROUND

Pulmonary tuberculosis (PTB) is frequently associated with chronic respiratory impairment despite microbiological cure. There are only a few clinical research studies that describe the course, type and severity as well as associated risk factors for lung impairment (LI) in TB patients.

METHODS

A prospective cohort study was conducted at TB Research Clinic of Instituto Nacional de Saúde in Mavalane, Maputo, from June 2014 to June 2016. PTB patients were prospectively enrolled and followed for 52 weeks after TB diagnosis. Lung function was evaluated by spirometry at 8, 26 and 52 weeks after TB treatment initiation, and spirometric values of below the lower limit of normality were considered as LI. Descriptive statistical analysis was performed to summarize the proportion of patients with different lung outcomes at week 52, including type and severity of LI. Risk factors were analysed using multinomial regression analysis.

RESULTS

A total of 69 PTB patients were enrolled, of which 62 had a valid spirometry result at week 52 after TB treatment start. At week 8, 26 and 52, the proportion of patients with LI was 78, 68.9 and 64.5%, respectively, and 35.5% had moderate or severe LI at week 52. The majority of patients with LI suffered from pulmonary restriction. Female sex, low haemoglobin and heavy smoking were significantly associated with LI.

CONCLUSION

Moderate or severe LI can be observed in a third of cured TB patients. Further research is urgently needed to gain deeper insight into the characteristics of post TB LI, the causal pathways and potential treatment strategies.

Patient outcomes associated with post-tuberculosis lung damage in Malawi: a prospective cohort study

BACKGROUND

Post-tuberculosis lung damage (PTLD) is a recognised consequence of pulmonary TB (pTB). However, little is known about its prevalence, patterns and associated outcomes, especially in sub-Saharan Africa and HIV-positive adults.

METHODS

Adult (≥15 years) survivors of a first episode of pTB in Blantyre, Malawi, completed the St George's Respiratory Questionnaire, 6-minute walk test, spirometry and high-resolution CT (HRCT) chest imaging at TB treatment completion. Symptom, spirometry, health seeking, TB-retreatment and mortality data were collected prospectively to 1 year. Risk factors for persistent symptoms, pulmonary function decline and respiratory-related health-seeking were identified through multivariable regression modelling.

RESULTS

Between February 2016 and April 2017, 405 participants were recruited. Median age was 35 years (IQR: 28 to 41), 77.3% (313/405) had had microbiologically proven pTB, and 60.3% (244/403) were HIV-positive. At pTB treatment completion, 60.7% (246/405) reported respiratory symptoms, 34.2% (125/365) had abnormal spirometry, 44.2% (170/385) had bronchiectasis ≥1 lobe and 9.4% (36/385) had ≥1 destroyed lobe on HRCT imaging. At 1 year, 30.7% (113/368) reported respiratory symptoms, 19.3% (59/305) and 14.1% (43/305) of patients had experienced declines in FEV₁ or FVC of ≥100 mL, 16.3% (62/380) had reported ≥1 acute respiratory event and 12.2% (45/368) had symptoms affecting their ability to work.

CONCLUSIONS

PTLD is a common and under-recognised consequence of pTB that is disabling for patients and associated with adverse outcomes beyond pTB treatment completion. Increased efforts to prevent PTLD and guidelines for management of established disease are urgently needed. Low-cost clinical interventions to improve patient outcomes must be evaluated.

Simvastatin Enhances the Immune Response Against Mycobacterium tuberculosis

Tuberculosis remains a serious threat worldwide. For this reason, it is necessary to identify agents that shorten the duration of treatment, strengthen the host immune system, and/or decrease the damage caused by the infection. Statins are drugs that reduce plasma cholesterol levels and have immunomodulatory, anti-inflammatory and antimicrobial effects. Although there is evidence that statins may contribute to the containment of Mycobacterium tuberculosis infection, their effects on peripheral blood mononuclear cells (PBMCs) involved in the immune response have not been previously described. Using PBMCs from 10 healthy subjects infected with M. tuberculosis H37Rv, we analyzed the effects of simvastatin on the treatment of the infections in an in vitro experimental model. Direct quantification of M. tuberculosis growth (in CFU/mL) was performed. Phenotypes and cell activation were assessed via multi-color flow cytometry. Culture supernatant cytokine levels were determined via cytokine bead arrays. The induction of apoptosis and autophagy was evaluated via flow cytometry and confocal microscopy. Simvastatin decreased the growth of M. tuberculosis in PBMCs, increased the proportion of NKT cells in culture, increased the expression of co-stimulatory molecules in monocytes, promoted the secretion of the cytokines IL-1β and IL-12p70, and activated apoptosis and autophagy in monocytes, resulting in a significant reduction in bacterial load. We also observed an increase in IL-10 production. We did not observe any direct antimycobacterial activity. This study provides new insight into the mechanism through which simvastatin reduces the mycobacterial load in infected PBMCs. These results demonstrate that simvastatin activates several immune mechanisms that favor the containment of M. tuberculosis infection, providing relevant evidence to consider statins as candidates for host-directed therapy. They also suggest that future studies are needed to define the roles of statin-induced anti-inflammatory mechanisms in tuberculosis treatment.

Morbidity and mortality up to 5 years post tuberculosis treatment in South Africa: A pilot study

BACKGROUND

A high risk of tuberculosis (TB), chronic lung disease, and mortality have been reported among people with a history of previous TB treatment, but data from high-incidence settings remain limited. The aim of this study was to characterize general morbidity and mortality among adults who had successfully completed TB treatment in the past 5 years in a high-incidence setting in South Africa.

METHODS

Adults (≥18 years) who had completed treatment for pulmonary TB between 2013 and 2017 were randomly selected from TB treatment registers. Household visits were conducted to locate and interview former TB (FTB) patients, and bacteriological testing for TB was offered. Additional data sources were used to ascertain the vitality status of FTB patients who could not be located.

RESULTS

Addresses were located for 200 of the 223 FTB patients sampled and 89 FTB patients were contacted of whom 51 agreed to be interviewed. Approximately half reported persistent respiratory symptoms, such as shortness of breath and wheezing, and repeated lung infections. One (3.6%) of 28 patients who provided a sputum sample had culture-positive TB and another two were currently on re-treatment for TB. Fifteen deaths post treatment were ascertained, resulting in a standardized mortality ratio of 3.8 (95% confidence interval 2.3-6.3) after successful TB treatment relative to the general population.

CONCLUSIONS

In this high-incidence setting, locating and interviewing FTB patients was challenging. The study findings are consistent with a high rate of respiratory disease, including recurrent TB, and substantially elevated mortality among FTB patients.