Agreement between observed and predicted postoperative forced expiratory volume in one second, forced vital capacity, and diffusing capacity for carbon monoxide after anatomic lung resection.

Background: Despite its importance in clinical practice, clinical guideline pathway selection and as an outcome in clinical trials, little work has been undertaken to understand the agreement between expected lung function loss and actual observed values. This is particular pertinent in view of the unexpected findings of JCOG 0802 and CALBG 140503 demonstrating no clinically meaningful difference in lung function loss between the sub-lobar resection and lobectomy arm. Methods: We performed a retrospective analysis on preoperative and postoperative forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and diffusing capacity for carbon monoxide (DLCO) collated from 158 patients who underwent anatomical lung resection between January 2013 to July 2023. Patient's true preoperative and postoperative lung function was obtained via formal lung function testing while predicted postoperative lung function was derived using the 20-segment counting method. Longitudinal postoperative lung function analysis demonstrated sufficient stability over time. A formal testing of agreement between predicted and true postoperative lung function was undertaken using the Bland and Altman method and graphically demonstrated using scatter plots. We defined a deviation of more than 5% as a clinically minimally important difference. Results: Scatter plots for effort-dependent measures suggested the tendency for underprediction (observed values were higher than predicted) for FEV1 and FVC but good agreement for DLCO. Formal agreement confirmed mean difference for FEV1 was -9.84% [95% confidence interval (CI): -39.33% to 19.65%], FVC -11.39% (95% CI: -50.14% to 27.36%) and DLCO -4.83% (95% CI: -25.59% to 15.92%). Conclusions: Our study demonstrated that effort-dependent parameters of lung function including FEV1 and FVC tends to overestimate the amount of lung function loss after anatomic lung resection, clinicians should be cautious in using these measures to determine suitability of surgery based on current established guidelines. However, independent measures such as DLCO demonstrate good agreement suggesting that predicted lung tissue loss is consistent with a 20-segment lung model.