Chest X-ray for predicting mortality and the need for ventilatory support in COVID-19 patients presenting to the emergency department

Abstract

Objectives: To evaluate the inter-rater agreement of chest X-ray (CXR) findings in coronavirus disease 2019 (COVID-19) and to determine the value of initial CXR along with demographic, clinical, and laboratory data at emergency department (ED) presentation for predicting mortality and the need for ventilatory support.

Methods: A total of 340 COVID-19 patients who underwent CXR in the ED setting (March 1-13, 2020) were retrospectively included. Two reviewers independently assessed CXR abnormalities, including ground-glass opacities (GGOs) and consolidation. Two scoring systems (Brixia score and percentage of lung involvement) were applied. Inter-rater agreement was assessed by weighted Cohen's kappa (κ) or intraclass correlation coefficient (ICC). Predictors of death and respiratory support were identified by logistic or Poisson regression.

Results: GGO admixed with consolidation (n = 235, 69%) was the most common CXR finding. The inter-rater agreement was almost perfect for type of parenchymal opacity (κ = 0.90), Brixia score (ICC = 0.91), and percentage of lung involvement (ICC = 0.95). The Brixia score (OR: 1.19; 95% CI: 1.06, 1.34; p = 0.003), age (OR: 1.16; 95% CI: 1.11, 1.22; p < 0.001), PaO₂/FiO₂ ratio (OR: 0.99; 95% CI: 0.98, 1; p = 0.002), and cardiovascular diseases (OR: 3.21; 95% CI: 1.28, 8.39; p = 0.014) predicted death. Percentage of lung involvement (OR: 1.02; 95% CI: 1.01, 1.03; p = 0.001) and PaO₂/FiO₂ ratio (OR: 0.99; 95% CI: 0.99, 1.00; p < 0.001) were significant predictors of the need for ventilatory support.

Conclusions: CXR is a reproducible tool for assessing COVID-19 and integrates with patient history, PaO₂/FiO₂ ratio, and SpO₂ values to early predict mortality and the need for ventilatory support.

Key points: • Chest X-ray is a reproducible tool for assessing COVID-19 pneumonia. • The Brixia score and percentage of lung involvement on chest X-ray integrate with patient history, PaO₂/FIO₂ ratio, and SpO₂ values to early predict mortality and the need for ventilatory support in COVID-19 patients presenting to the emergency department.

Keywords: COVID-19; Radiography; Severe acute respiratory syndrome coronavirus 2.

Fig. 1

Correlation and agreement between chest X-ray findings obtained by two independent reviewers in 340 patients with confirmed COVID-19. Correlation and Bland-Altman plots show the agreement in Brixia score (a, b) and percentage of lung involvement (c, d) between the reference reviewer (reviewer 1, a thoracic radiologist with 5 years of experience) and reviewer 2 (a fourth-year radiology resident). In correlation plots, the dashed line denotes the line of perfect concordance, while the solid line denotes the reduced major axis. In Bland-Altman plots, the solid line denotes mean difference, while dashed lines denote mean difference ± 2 standard deviations

Fig. 2

Chest X-ray (CXR) findings at the emergency department presentation in two patients with confirmed COVID-19 and opposite outcomes. a CXR shows bilateral, mostly peripheral, ground-glass opacities (GGOs) admixed with consolidation (consolidation-predominant) (arrowheads). Reviewer 1 assigned a Brixia score of 14 and a percentage of lung involvement of 60%. Reviewer 2 assigned a Brixia score of 15 and a percentage of lung involvement of 50%. This patient had a prolonged stay in the intensive care unit and died 11 days after presenting to the emergency department. b CXR shows bilateral GGOs, either pure (empty arrowheads) or admixed with consolidation (GGO-predominant) (solid arrowhead). Reviewer 1 assigned a Brixia score of 6 and a percentage of lung involvement of 30%. Reviewer 2 assigned a Brixia score of 5 and a percentage of lung involvement of 25%. This patient was discharged from the emergency department after a short-term observation with home care and isolation precautions and was alive at the end of the study period

Fig. 3

Survival curves related to 340 patients with confirmed COVID-19, grouped by demographic variables (a: age, b: sex), PaO₂/FiO₂ ratio (c), and chest X-ray findings at presentation to the emergency department (d: Brixia score, e: number of lung zones involved, f: percentage of lung involvement), over a median of 63 days observation time. Shadows denote 95% confidence intervals, while p denotes the significance of the difference between strata at log-rank test. PaO₂/FiO₂ ratio, ratio of partial pressure of oxygen to fraction of inspired oxygen

Fig. 4

Distribution of age (a), PaO₂/FiO₂ ratio (b), and CXR findings (c: Brixia score, d: percentage of lung involvement, e: number of lung zones involved) at presentation to the emergency department by the most invasive respiratory support employed in 340 patients with confirmed COVID-19. CXR, chest X-ray; ED, emergency department; PaO₂/FiO₂ ratio, ratio of partial pressure of oxygen to fraction of inspired oxygen; OM, oxygen mask; CPAP/NIV, continuous positive airway pressure/noninvasive mechanical ventilation; IV, invasive mechanical ventilation