Prognostic value of the 6-minute-walk-test derived attributes in patients with IPF

<bold>Background:</bold> Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease. From the 6-minute walk test (6MWT), a decreased 6-minute walk distance (6MWD) and an exercise-induced oxygen desaturation (SpO₂-nadir) are known predictors of mortality in patients with IPF. Whether this is still true for IPF patients in the era of mortality-lowering antifibrotic drugs remains currently unknown. Therefore, this study aimed to evaluate whether 6MWT-derived attributes are associated with two-year survival when antifibrotics were introduced as part of standard IPF-care. <bold>Methods:</bold> This real-world data-study included patients with IPF with a 6MWT between 2015-2020, and used composite outcome: mortality or lung transplantation within 2 years of follow-up. Data were collected systematically, including demographics, pulmonary function tests, comorbidities, medications and 6MWT. The prediction attributes of 6MWT were studied with a Cox Proportional-Hazards model and Kaplan-Meier survival curves. The best discriminating attribute to predict mortality was added to the prediction model Gender-Age-Physiology (GAP). <bold>Results:</bold> In 216 patients, 2-year transplant-free survival cutoff points were identified for the 6MWD (≥413 m), 6MWD %predicted (≥83%), SpO₂-nadir (≥86%) and distance-saturation-product (≥374 m%), with the best discriminative value for SpO₂-nadir (AUC: 0.761). 2-Year survival percentage of patients with SpO₂-nadir below or above threshold (86%) was 37.1% and 80.0%, respectively. The new GAP-SpO₂-nadir showed an improvement in predictive power. <bold>Conclusions:</bold> Patients with IPF who have a SpO₂-nadir <86% have worse prognosis. Addition of SpO₂-nadir to the GAP model seems promising for use in clinical care of IPF patients.