Visual HRCT Score to Determine Severity and Prognosis of Idiopathic Pulmonary Fibrosis

Abstract

Introduction: High-resolution computed tomography (HRCT) is an essential technique for the diagnosis and follow-up of idiopathic pulmonary fibrosis (IPF), but it is not routinely used to evaluate severity. A semi-quantitative HRCT score was developed to determine its relation with physiologic variables, to assess severity and fibrosis progression, and to establish prognostic factors. Methods: The HRCTs of 48 newly diagnosed IPF patients were assessed. Reticular pattern, ground-glass opacities, distortion and honeycomb patterns were scored by two independent radiologists to obtain these scores and the Total Score of Fibrosis. Its relation with pulmonary function tests, the 6-minute walking test (6MWT) and air blood gases was evaluated, and with the survival and identification of the worse prognosis factors. The lower HRCT level (everything below the highest point of the right diaphragm) was independently assessed to evaluate differences. Results: The Honeycomb Score (HS) correlated with DLCO% (r = -0.50, p < 0.001) and KCO% (r = -0.55, p < 0.001). The Total Score (TS) correlated with DLCO% (r = -0.55, p < 0.001) and KCO% (r = -0.50, p < 0.001). Final SatO2 in the 6MWT correlated with the TS (r = -0.45, p < 0.01), and desaturation correlated with both HS (r = -0.34, p < 0.05) and TS (r = -0.45, p < 0.01). Survival was 42 (37-48) months. DLCO < 40 (p = 0.005) and the TS of Fibrosis ≥ 20 (p = 0.03) were independent predictors of mortality. In the lower HRCT level assessment HS correlated with DLCO (r = -0.533; p < 0.001), KCO (r = -0.426; p < 0.01) and CPI (r = 0.505; p < 0.001), and also the TS correlated with both DLCO (r = -0.362; p < 0.01) and KCO (r = -0.481; p < 0.001); the HS was an independent mortality factor (p = 0.015) at this level. Conclusions: A semi-quantitative HRCT score is useful for determining severity upon diagnosis and for predicting IPF progression, and it correlates well with physiologic variables. DLCO < 40 and the TS of Fibrosis ≥ 20 were independent mortality predictors. The honeycomb score at lower HRCT levels determined mortality.