Treatment success, but living with the consequences of post-tuberculosis sequelae

The sequelae of pulmonary tuberculosis (TB) have been variably defined as loss of lung function (typically in a restrictive or mixed obstructive/ restrictive pattern),^1,2 decrease in exercise capacity, and/or chronic respiratory symptoms resulting from TB-associated interstitial and architectural changes.^3–7 The severity of these manifestations can cover a broad spectrum, and often co-exist with other forms of chronic respiratory disease, including tobacco smoking-related lung disease (smoking has long been associated with TB),⁸ bronchiectasis related to prior pneumonias, and nontuberculous mycobacterial infection, among others. Nevertheless, a tissue-destructive immunopathology has been identified, which is beneficial to the Mycobacterium tuberculosis lifecycle, and involves upregulated collagenase and pro-inflammatory cytokines.⁹

In this issue of the Journal, Muñoz-Torrico et al. assessed lung function using body plethysmography and single-breath carbon monoxide diffusion capacity (DLCO), the 6-minute walk test (6MWT), and quality of life among a convenience sample of patients recently completing TB treatment in a low-to middle-burden setting for TB.¹⁰ The authors found that 65% of those completing TB treatment had some form of functional impairment, most commonly mild airway obstruction and a DLCO less than the lower limit of normal (which was adjusted for altitude but not for hemoglobin level). They also observed that impairment was greater among those treated for drug-resistant, rather than drug-susceptible TB. Assessment of the generalizability of these findings, however, must be balanced against the limited size of the study, the large proportion of patients with a history of smoking and sampling from reference centers specializing in pulmonary rehabilitation. Nevertheless, these findings are congruent with the literature, suggesting that in spite of completing treatment, a large proportion of TB patients have significant post-TB respiratory impairment. Although this is likely to be a major contributor to the global burden of chronic lung disease involving millions of TB survivors annually, the full impact of individual episodes of TB among various patient populations remains unclear. Evidence to date is based on largely cross-sectional, retrospective, or registry studies with high risks of bias.²

In an accompanying article, Visca et al. nicely summarize the evidence for pulmonary rehabilitation in treating post-TB exercise capacity limitation and poor quality of life.¹¹ Pulmonary rehabilitation is a comprehensive intervention based on a thorough patient assessment, followed by patient-tailored therapies, and includes exercise training, education, and behavior change: it is designed to improve the physical and psychological condition of people with chronic respiratory disease and to promote long-term adherence to health-enhancing behaviours.¹² With regard to the duration of a program, 8–10 weeks has been found to lead to clinically relevant improvements in daily symptoms (e.g., dyspnea, fatigue, anxiety and/or depression), physical capacity, and quality of life in patients, without a significant change in the degree of airflow limitation.^12–14 Despite the reported benefits (mostly in patients with chronic obstructive diseases), pulmonary rehabilitation is grossly underutilized and is frequently inaccessible to patients because of limited funding for such programs, insufficient health system reimbursement for pulmonary rehabilitation, suboptimal use of the program by suitable patients and limited training opportunities for pulmonary rehabilitation professionals.¹⁵ The introduction of home- or community-based pulmonary rehabilitation programs as an alternative model has the potential to improve access and uptake, while reducing health care utilisation.^16–18 Given these barriers and resource limitations, it will be critical to use simplified screening tools (such as the five-repetition sit-to-stand test¹⁹) with the potential to cost-effectively identify individuals with post TB sequelae that are most amenable to pulmonary rehabilitation.

TB patients who are successfully treated can no longer simply be relegated to the ‘win’ column and forgotten.^20,21 The global burden of chronic lung disease likely to be attributable to TB highlights the need for prevention over cure, and supports calls for improving the basic provisions of health care in high-burden countries.⁴ Finally, this all adds to the rationale for the call by Harries et al.²¹ for a ‘fourth 90′—ensuring that 90% of all people successfully completing treatment for TB can have a good health-related quality of life.