COVID-19 pneumonia: Perfusion abnormalities shown on subtraction CT angiography in apparently well-ventilated lungs. A prospective cohort study

Purpose: To evaluate whether a subtraction CT angiography (sCTA) perfusion score may have prognostic value in patients with COVID-19 pneumonia. Method: This prospective cohort study included adult patients with RT-PCR-confirmed SARS-CoV-2 infection admitted to the ED and a sCTA performed within 24 h of admission between June and September 2020. Perfusion abnormalities (PA) in areas of apparently spared lung parenchyma on conventional CT images were assessed with sCTA perfusion score. Airspace disease extension was assessed with CT severity scores, which were then correlated with clinical outcomes (admission to ICU, requirement of IMV, and death). Inter-rater reliability (IRR) was assessed using Cohen's Kappa. Independent predictors of adverse outcomes were evaluated by multivariable logistic regression analyses using the Hosmer and Lemeshow's test. Results: 191 patients were included: 112 males (58%), median age of 60.8 years (SD ± 16.0). The IRR was very high (median Kappa statistic: 0.95). No association was found between perfusion CT scores and D-dimer levels (Kendall's Tau-B coefficient = 0.08, p = 0.16) or between PaO₂/FiO₂ ratios and D-dimer levels (Kendall's Tau-B coefficient = −0.10, p = 0.07). Multivariate analyses adjusting for parenchymal disease extension, vascular beaded appearance, pulmonary embolism, sex, and age showed that severe PA remained a significant predictor for ICU admission (AOR: 6.25, 95% CI 2.10–18.7, p = 0.001). The overall diagnostic capacity of this model was adequate (ROC AUC: 0.83; 95% CI 0.77–0.89). Conclusions: The assessment of pulmonary perfusion abnormalities in areas of apparently spared lung parenchyma on conventional CT images via sCTA perfusion scoring has prognostic value in COVID-19 pneumonia.