Predicting Outcome in Idiopathic Pulmonary Fibrosis: Addition of Fibrotic Score at Thin-Section CT of the Chest to Gender, Age, and Physiology Score Improves the Prediction Model

Anurag Chahal; Roozbeh Sharif; Jubal Watts; Joao de Andrade; Tracy Luckhardt; Young-Il Kim; Rekha Ramchandran; Sushilkumar Sonavane

doi:10.1148/ryct.2019180029

Predicting Outcome in Idiopathic Pulmonary Fibrosis: Addition of Fibrotic Score at Thin-Section CT of the Chest to Gender, Age, and Physiology Score Improves the Prediction Model

Radiol Cardiothorac Imaging. 2019 Jun 27;1(2):e180029. doi: 10.1148/ryct.2019180029. eCollection 2019 Jun.

Authors

Anurag Chahal¹, Roozbeh Sharif¹, Jubal Watts¹, Joao de Andrade¹, Tracy Luckhardt¹, Young-Il Kim¹, Rekha Ramchandran¹, Sushilkumar Sonavane¹

Affiliation

¹ Department of Radiology, Cardiopulmonary Section (A.C., J.W., S.S.), Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine (R.S., J.d.A., T.L., Y.I.K., R.R.), and Division of Preventive Medicine (Y.I.K., R.R.), University of Alabama at Birmingham, 619 19th St S, Birmingham AL 35249; Pulmonary and Critical Care Medicine, Houston Methodist Hospital and Weill Cornell School of Medicine, Houston, Tex (R.S.); and Radiology of Huntsville, Huntsville, Ala (J.W.).

Abstract

Purpose: To assess the impact of adding thin-section CT-derived semiquantitative fibrotic score to gender, age, and physiology (GAP) model for predicting survival in idiopathic pulmonary fibrosis (IPF).

Materials and methods: In this retrospective study of 194 patients with IPF, primary outcome was transplant-free survival. Two thoracic radiologists visually estimated the percentage of reticulation and honeycombing at baseline thin-section CT, which were added to give fibrotic score. For analysis, fibrotic score cutoff (x) determined by using receiver operating characteristic analysis categorized patients into group A (<x) and group B (≥x). Another categorization based on GAP score created group 1 (score 0-3) and group 2 (score >3). Combining the above categories gave four groups (A1, A2, B1, B2). Kaplan-Meier survival analysis was performed with comparison statistics (log-rank test), and hazard ratios were calculated by using the Cox model.

Results: The study patients included 141 men (72.7%), with average age of 66.1 years ± 9.1 (standard deviation). Eighty-four patients (43.3%) has stage I disease with a median follow up of 3.3 years. The interobserver agreement for thin-section CT fibrotic score was substantial (83.3%; κ = 0.64). The optimal cutoff for fibrotic score was 25% (x), with area under the curve of 0.654 (95% confidence interval [CI]: 0.569, 0.74). Survival for group A1 was significantly better than in the other three groups (P < .001). The hazard ratios for respective groups were as follows: B1 was 4.03 (95% CI: 2.02, 8.07), A2 was 4.10 (95% CI: 1.89, 8.87), and B2 was 5.62 (95% CI: 2.86, 11.06) (P < .001 for all). Within the group with GAP score less than or equal to 3 (A1, B1), participants with higher fibrotic score (B1) had four times the increased risk of death or transplantation (P < .001).

Conclusion: Incorporating semiquantitative fibrotic score from thin-section CT to GAP score provides an improved prediction model for survival in idiopathic pulmonary fibrosis.© RSNA, 2019See also the commentary by Chung in this issue.

2019 by the Radiological Society of North America, Inc.