A multidimensional index with SpO₂ at rest for predicting progressive pulmonary fibrosis

To develop a multidimensional weighted score for progressive fibrotic interstitial lung disease (fILD) on the basis of mortality risk and compare the score with the progressive pulmonary fibrosis (PPF) guideline and Efficacy and Safety of Nintedanib in Patients with Progressive Fibrosing Interstitial Lung Disease (INBUILD) trial criteria.

This was a multicenter retrospective cohort study of fILD patients evaluated from January of 2008 to January of 2020. Disease progression was evaluated by changes in dyspnea, HRCT findings, FVC, DL_CO, and SpO₂. Associations between the disease progression criteria and survival were analyzed by means of Kaplan-Meier curves. By means of univariate Cox regression, a score was determined on the basis of the relative weights for the progression criteria. The score was derived and tested within the same cohort. We compared the score with the PPF guideline and INBUILD trial criteria.

A total of 380 patients were evaluated. Cox regression was used in order to assign points to the progression criteria: a decrease of < 90% in SpO₂ at rest (2 points); disease progression on HRCT (2 points); worsening dyspnea (1 point); a decrease ≥ 3% in SpO₂ at rest (1 point); a decrease of 5-9% in FVC (1 point); and a decrease ≥ 10% in FVC (2 points). The final score was categorized as follows: low risk, 0-2 points (n = 244), median survival = undetermined; intermediate risk, 3-4 points (n = 61), median survival = 81 months (95% CI, 65-96); and high risk, ≥ 5 points (n = 75), median survival = 57 months (95% CI, 38-75; p < 0.001). A total of 136 patients (35.8%) showed disease progression. Kappa concordance was 0.92 (p < 0.001) for the PPF guideline criteria and 0.81 (p < 0.001) for the INBUILD trial criteria.

A multidimensional weighted score allows us to estimate the risk of progressive fILD. When dichotomized, the concordance with the PPF guideline and INBUILD trial criteria is high. External validation is required before routine clinical application.