Correlation between lung function tests and peak oxygen consumption in post-TB lung disease

BACKGROUND: After TB treatment, many patients have post-TB lung disease (PTLD), associated with increased mortality and morbidity. Nevertheless, relationships between lung function testing and exercise capacity in people with PTLD are poorly understood.

METHODS: This single-centre study investigated the association between lung function testing and peak oxygen consumption (VO₂peak) and percentage-predicted VO₂peak (VO₂peak (%pred)) in adults with PTLD investigated for surgery.

RESULTS: Eighty-two patients (52 males, 30 females) with a mean age of 43.2 years (SD 11.3) were included. Spirometric values of forced vital capacity (FVC) percentage predicted (%pred) and forced expiratory volume in 1 sec (FEV₁) %pred suggested significant correlations with VO₂peak (%pred) (P < 0.001 and P < 0.001), whereas FEV₁/FVC did not. Diffusing capacity for carbon monoxide (DL_CO) %pred also correlated significantly with VO₂peak (%pred) (P = 0.002). However, the magnitude of all significant correlation coefficients were weak. No significant correlations for any plethysmographic values with VO₂peak (%pred) could be robustly concluded. Correlations with VO₂peak (ml/kg/min) for most physiological variables were less robust than for VO₂peak (%pred).

CONCLUSIONS: Although statistically significant, the correlations between any measure of lung function and VO₂peak or VO₂peak (%pred) were weak, with only FVC correlation coefficient surpassing 0.50.