Consolidation-to-ground-glass opacity ratio on chest CT as a prognostic marker for critical outcomes in COVID-19: a retrospective cohort study.

BACKGROUND: Computed tomography (CT)-based quantification of coronavirus disease 2019 (COVID-19) pneumonia is widely performed, and total pneumonia volume, ground-glass opacity (GGO), and consolidation affect disease severity. However, there is insufficient information on how consolidation to GGO (C/G) ratio correlates with clinical characteristics including disease severity and complications in COVID-19 patients. METHODS: This retrospective cohort study included 1,194 hospitalized patients with COVID-19 from four member hospitals of the Japan COVID-19 Task Force. Critical outcomes were defined as conditions requiring high-flow oxygen or invasive mechanical ventilation, or death. Patients were divided into two groups based on %pneumonia (percentage of pneumonia volume divided by total lung volume) using receiver operating characteristic curve, and those with high %pneumonia were further divided into two groups based on C/G ratio. Critical outcomes and complications were then compared between high and low C/G ratio groups. RESULTS: The optimal cutoff value of %pneumonia to predict critical outcomes was 17.1%, classifying the included patients into low (Group 1, n = 900) and high (n = 294) %pneumonia groups. The optimal cutoff value of C/G ratio was 0.202, classifying patients in the high %pneumonia group into two groups: low (Group 2, n = 192) and high C/G (Group 3, n = 102) ratio groups. The incidence of critical outcomes was stair-step high in all three groups (2.1%, 21.4%, and 37.3%, respectively). Multivariable analysis revealed an independent relationship between C/G ratio and critical outcomes from other known risk factors (adjusted odds ratio: 1.92, 95% confidential interval: 1.03-3.59, P = 0.040). Group 3 also showed significantly higher serum C-reactive protein (Group 1: 2.96 mg/dL, Group 2: 8.90 mg/dL, Group 3: 11.4 mg/dL) and procalcitonin (Group 1: 0.16 ng/mL, Group 2: 0.25 ng/mL, Group 3: 1.19 ng/mL) levels and incidence of bacterial infection (Group 1: 5.6%, Group 2: 10.4%, Group 3: 20.3%), compared with other groups. CONCLUSIONS: CT-density analysis of COVID-19 pneumonia in a large patient population showed that C/G ratio was a significant predictor of critical outcomes and useful for prognosis evaluation.