Lung function impairment at pulmonary TB and HIV/TB diagnosis: a South African cross-sectional cohort analysis

Objectives To characterise the patterns and severity of impaired lung function at pulmonary tuberculosis (TB) diagnosis and assess the impact of HIV co-infection on TB-associated lung injury. Setting A cross-sectional analysis of adults with and without HIV who presented with newly diagnosed drug-susceptible pulmonary TB in Johannesburg, South Africa. Participants A total of 258 adults who were newly diagnosed with drug-susceptible pulmonary TB underwent comprehensive pulmonary function tests (PFT). Primary and secondary outcome measures Five key PFT manoeuvres were evaluated: forced expiratory volume in one second (FEV1), forced vital capacity (FVC), FEV1/FVC, total lung capacity (TLC) and haemoglobin-corrected diffusion capacity of the lungs for carbon monoxide (DLCO). Three primary outcomes were modelled: (1) normal versus abnormal lung function, defined as any key PFT manoeuvre z-score < lower limit of normal, (2) continuous z-scores for each PFT and (3) clinical patterns of lung function (normal, restriction, obstruction, mixed disorder and isolated low DLCO). Secondary outcomes included respiratory health-related quality-of-life measures assessed using the St. George’s Respiratory Questionnaire (SGRQ). Results HIV/TB co-infection was associated with lower odds of any abnormal lung function (adjusted OR (aOR) 0.43, 95% CI 0.24 to 0.74) and lower odds of restrictive (aOR 0.46, 95% CI 0.24 to 0.87) and mixed patterns (aOR 0.22, 95% CI 0.07 to 0.66) compared with those with TB alone. HIV co-infection was also associated with better FEV1, FVC, FEV1/FVC and TLC z-scores. While those with HIV had less severe radiographic disease, respiratory symptoms were similar between groups (SGRQ total score: HIV-negative 22 (IQR: 13–38) vs HIV-positive 26 (IQR: 8–44), p>0.9). Conclusions Adults with HIV/TB co-infection demonstrated a distinct clinical phenotype of TB-associated lung injury at TB diagnosis characterised by less severe radiographic and lung function impairment compared with those without HIV.