CT ‐determined pulmonary artery to aorta ratio as a predictor of elevated pulmonary artery pressure and survival in idiopathic pulmonary fibrosis

Background and objective Elevated mean pulmonary artery pressure ( mPAP ) is a significant prognostic indicator in idiopathic pulmonary fibrosis ( IPF ). It has been reported that the computed tomography‐determined ratio of the diameter of the pulmonary artery to the aorta ( PA :A) is correlated with mPAP in various respiratory diseases. However, in patients with IPF , whether the PA :A can be used to predict elevated mPAP and the prognostic value of the PA :A has not been fully evaluated. Methods We conducted a single‐centre, observational study of 177 consecutive IPF patients who underwent right heart catheterization. We examined the association between the PA :A and mPAP in these patients, and performed a receiver operating characteristic ( ROC ) analysis to test the diagnostic accuracy of the PA :A in predicting mPAP  > 20 mm Hg (pulmonary hypertension ( PH ) or borderline PH ) in relation to survival. Results In a multivariate linear regression analysis, the PA :A, 6‐min walk distance and diffusion capacity for carbon monoxide ( DL CO ) % predicted were independent explanatory variables of elevated mPAP ( P  < 0.0001, P  = 0.009 and P  = 0.002, respectively). ROC analysis revealed a PA :A > 0.9 to be optimal for predicting mPAP  > 20 mm Hg (area under the curve ( AUC ) = 0.75; 95% CI : 0.65–0.84). Patients with a PA :A > 0.9 also had a worse prognosis ( P  = 0.009). Conclusion Measurement of the PA :A is a useful and convenient method to predict elevated mPAP in IPF at initial evaluation. Moreover, a PA :A >0.9 was found to be an indicator of worse prognosis.