Three-minute walk test as a practical screening tool for detecting exertional hypoxemia in fibrotic interstitial lung disease: a real-world cohort study.

Fibrotic interstitial lung disease (F-ILD) is associated with substantial morbidity and mortality, in which exertional hypoxemia represents a key marker of disease severity. Although the six-minute walk test (6MWT) is the reference standard for its assessment, routine use is often limited by practical constraints. This study aimed to evaluate whether the three-minute walk test (3MWT) could serve as a pragmatic screening tool for detecting exertional hypoxemia.In this real-world cohort study, 82 patients with multidisciplinary discussion-confirmed F-ILD were enrolled. All patients underwent both 3MWT and 6MWT, along with pulmonary function testing. Correlations between oxygenation indices and the predictive performance of 3MWT parameters for identifying desaturation during the 6MWT (nadir SpO₂ <90%) were analyzed. Moderate correlations were observed between 3MWT and 6MWT for resting SpO₂ (r = 0.65), nadir SpO₂ (r = 0.71), and ΔSpO₂ (r = 0.68) (all p < 0.001). Patients with exertional desaturation (nadir SpO₂ <90%) during the 6MWT demonstrated lower nadir SpO₂ and greater ΔSpO₂ during the 3MWT. Receiver operating characteristic analysis showed that ΔSpO₂ >4.5% and nadir SpO₂ <90.5% during the 3MWT provided optimal discrimination (AUC 0.83). The 3MWT provides clinically relevant oxygenation information that correlates with standard 6MWT parameters and may serve as a practical screening and triage tool to identify patients at risk of exertional hypoxemia. It should be considered complementary to, rather than a replacement for, the 6MWT.