Transition from Restrictive to Obstructive Lung Function Impairment During Treatment and Follow-Up of Active Tuberculosis

Brian W Allwood; Elizna Maasdorp; Grace J Kim; Christopher B Cooper; Jonathan Goldin; Richard N van Zyl-Smit; Eric D Bateman; Rodney Dawson

doi:10.2147/COPD.S219731

Transition from Restrictive to Obstructive Lung Function Impairment During Treatment and Follow-Up of Active Tuberculosis

Int J Chron Obstruct Pulmon Dis. 2020 May 11:15:1039-1047. doi: 10.2147/COPD.S219731. eCollection 2020.

Authors

Brian W Allwood^{1

2}, Elizna Maasdorp³, Grace J Kim^{4

5}, Christopher B Cooper⁶, Jonathan Goldin⁴, Richard N van Zyl-Smit², Eric D Bateman², Rodney Dawson²

Affiliations

¹ Division of Pulmonology, Department of Medicine, Stellenbosch University, Cape Town, South Africa.
² University of Cape Town Lung Institute, and Division of Pulmonology, Department of Medicine, University of Cape Town, Cape Town, South Africa.
³ DST/NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
⁴ Center for Computer Visions and Imaging Biomarkers, Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
⁵ Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, CA, USA.
⁶ Departments of Medicine and Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.

Abstract

Background: Pulmonary tuberculosis (PTB) is associated with many forms of chronic lung disease including the development of chronic airflow obstruction (AFO). However, the nature, evolution and mechanisms responsible for the AFO after PTB are poorly understood. The aim of this study was to examine the progression of changes in lung physiology in patients treated for PTB.

Methods: Immunocompetent, previously healthy, adult patients receiving ambulatory treatment for a first episode of tuberculosis were prospectively followed up with serial lung physiology and quantitative computed tomography (CT) lung scans performed at diagnosis of tuberculosis, 2, 6, 12 and 18 months during and after the completion of treatment.

Results: Forty-nine patients (median age 26 years; 37.2% males) were included, and 43 were studied. During treatment, lung volumes improved and CT fibrosis scores decreased, but features of AFO and gas trapping emerged, while reduced diffusing capacity (DLco) seen in a majority of patients persisted. Significant increases in total lung capacity (TLC) by plethysmography were seen in the year following treatment completion (median change 5.9% pred., P<0.01) and were driven by large increases in residual volume (RV) (median change +19%pred., P<0.01) but not inspiratory capacity (IC; P=0.41). The change in RV/TLC correlated with significant progression of radiological gas trapping after treatment (P=0.04) but not with emphysema scores. One year after completing treatment, 18.6% of patients had residual restriction (total lung capacity, TLC <80%pred), 16.3% had AFO, 32.6% had gas trapping (RV/TLC>45%), and 78.6% had reduced DLco.

Conclusion: Simple spirometry alone does not fully reveal the residual respiratory impairments resulting after a first episode of PTB. Changes in physiology evolve after treatment completion, and these findings when taken together, suggest emergence of gas trapping after treatment likely caused by progression of small airway pathology during the healing process.

Keywords: airflow obstruction; chronic obstructive pulmonary disease; computed tomography; lung function; post-tuberculosis; tuberculosis.

MeSH terms

Adult
Female
Follow-Up Studies
Humans
Lung / diagnostic imaging
Male
Pulmonary Disease, Chronic Obstructive*
Spirometry
Tuberculosis, Pulmonary* / diagnostic imaging
Tuberculosis, Pulmonary* / drug therapy

Grants and funding

Funding received from the University of Cape Town Lung Institute for funding the radiology component and Global Alliance for TB Drug Development for access to their bio-storage cohort. E.M. is funded by a Strategic Health Innovation Partnership (SHIP) grant from the South African (SA) Department of Science and Technology (DST) and SA Medical Research Council (SAMRC) to the South African Tuberculosis Bioinformatics Initiative (SATBBI), and E.B. received funding from the National Research Foundation (NRF).