Estimating COVID-19 Pneumonia Extent and Severity From Chest Computed Tomography

Front Physiol. 2021 Feb 15;12:617657. doi: 10.3389/fphys.2021.617657. eCollection 2021.

ABSTRACT

BACKGROUND: COVID-19 pneumonia extension is assessed by computed tomography (CT) with the ratio between the volume of abnormal pulmonary opacities (PO) and CT-estimated lung volume (CT_LV). CT-estimated lung weight (CT_LW) also correlates with pneumonia severity. However, both CT_LV and CT_LW depend on demographic and anthropometric variables.

PURPOSES: To estimate the extent and severity of COVID-19 pneumonia adjusting the volume and weight of abnormal PO to the predicted CT_LV (pCT_LV) and CT_LW (pCT_LW), respectively, and to evaluate their possible association with clinical and radiological outcomes.

METHODS: Chest CT from 103 COVID-19 and 86 healthy subjects were examined retrospectively. In controls, predictive equations for estimating pCT_LV and pCT_LW were assessed. COVID-19 pneumonia extent and severity were then defined as the ratio between the volume and the weight of abnormal PO expressed as a percentage of the pCT_LV and pCT_LW, respectively. A ROC analysis was used to test differential diagnosis ability of the proposed method in COVID-19 and controls. The degree of pneumonia extent and severity was assessed with Z-scores relative to the average volume and weight of PO in controls. Accordingly, COVID-19 patients were classified as with limited, moderate and diffuse pneumonia extent and as with mild, moderate and severe pneumonia severity.

RESULTS: In controls, CT_LV could be predicted by sex and height (adjusted R ² = 0.57; P < 0.001) while CT_LW by age, sex, and height (adjusted R ² = 0.6; P < 0.001). The cutoff of 20% (AUC = 0.91, 95%CI 0.88-0.93) for pneumonia extent and of 50% (AUC = 0.91, 95%CI 0.89-0.92) for pneumonia severity were obtained. Pneumonia extent were better correlated when expressed as a percentage of the pCT_LV and pCT_LW (r = 0.85, P < 0.001), respectively. COVID-19 patients with diffuse and severe pneumonia at admission presented significantly higher CRP concentration, intra-hospital mortality, ICU stay and ventilatory support necessity, than those with moderate and limited/mild pneumonia. Moreover, pneumonia severity, but not extent, was positively and moderately correlated with age (r = 0.46) and CRP concentration (r = 0.44).

CONCLUSION: The proposed estimation of COVID-19 pneumonia extent and severity might be useful for clinical and radiological patient stratification.

PMID:33658944 | PMC:PMC7917083 | DOI:10.3389/fphys.2021.617657