Lung Function Abnormalities Before and After Treatment of Pulmonary Tuberculosis in Selected Health Facilities in Dar Es Salaam

Abstract

Background: Tuberculosis (TB) causes the highest number of deaths worldwide as a single infection. Tanzania, reports more than 80,000 TB cases every year. However, in Tanzania post TB treatment lung disease has not been fully explored. This study aimed to document abnormalities in lung function at initiation and at the end of anti TB therapy and explore the associated factors among patients treated for first ever Pulmonary Tuberculosis in one of the five (5) selected TB clinics in Dar es Salaam. Methodology: A prospective longitudinal study was conducted in 5 tuberculosis (TB) clinics, in Dar es Salaam between August 2020 to May 2021. Newly diagnosed pulmonary TB (PTB) patients aged 15 years or above, were recruited upon written consent or accent where applicable. Patients were evaluated using spirometry at recruitment and at treatment completion. The outcome of interest was proportions of abnormal lung function; obstructive, restrictive and mixed lung function defects at recruitment and at TB treatment completion. Chi-square  2 test was used to compare the differences in proportions of lung function abnormalities. Paired t test was used to assess the change in lung functions and Log binomial regression model was used to determine factors associated with abnormal lung functions at treatment completion. All patients were treated as per national TB treatment guidelines with Rifampicin (R), Isoniazid (H), Pyrazinamide (Z) and Ethambutol (E). Results: A total of 332 patients with PTB were recruited. Overall 64.1% (n=213) of patients showed some form of abnormal lung function at treatment initiation. At treatment completion, abnormal lung function was observed among 47.3% (n=142). The median FEV1 (IQR) at the end of TB treatment was significantly higher, (2.33L ± 0.26) compared to the FEV1 at the start of treatment which was (2.18L ± 1.16) P= 0.001. Similarly, the median FVC (IQR) at the end of TB treatment had significantly increased 3.05L ± 0.31 compared to at the initiation of TB treatment (2.82L ± 1.5) P= 0.010. Being underweight, (RR: 1.49, 95% 1.13 - 1.95 CI; P<0.004), male sex (RR: 1.22, 95% CI 1.19 - 2.23 CI; P=0.004), cavitation (RR: 1.90, 95% CI 1.29 – 2.78, P = 0.02) and lung parenchymal fibrosis on chest X ray were RR: 2.16, 95% CI 1.32 – 3.53, P 0.001 were significantly associated with increased risk for abnormal lung functions at treatment completion. Conclusion: Six months anti-tuberculosis chemotherapy was associated with improvement in lung functions in a number of patients. However, about 1 out of 2 of our patients treated for tuberculosis had residual abnormality in lung function at the end of tuberculosis treatment. There is need for further studies to find additional agents that will enhance the effect of anti-tuberculosis chemotherapy in improving lung health. Secondly, patients treated for tuberculosis need longer follow up beyond the period of treatment. The appropriate length of follow up is a subject for further research.