COVID-19 chest CT and laboratory features of B.1.617.2 (Delta variant) vs B.1.1.7 (Alpha variant) surge: a single center case-control study

Purpose: To assess clinical, laboratory and radiological differences between Delta and Alpha SARS-CoV-2 variants.

Materials and methods: Twenty SARS-CoV-2 patients admitted from 30th of August to 30th of October 2021 (period with estimated highest prevalence of Delta variant circulation in Italy) were enrolled. Patients were matched in a 1:1 ratio with same gender and same age +/- 2 years controls admitted from 1st of September 2020 to 30th of January 2021 (predominant circulation of Alpha variant). Chest computed tomography (CT) were retrospectively evaluated. Main clinical parameters, radiological and laboratory findings were compared between two groups.

Results: Patients with probable Delta variant had significantly higher CT severity scores, lower PaO2/FiO2 ratio and higher C-reactive protein and lactate dehydrogenase levels at admission. On multivariate analysis, probable Delta variant infection was associated with higher CT severity score. Ground glass opacities and crazy paving patterns were more frequently noticed than consolidation, with the latter being more frequent in Delta cohort, even though not significantly. According to prevalent imaging pattern, the consolidation one was significantly associated with pregnancy (p=0.008).

Conclusions: Patients admitted during predominance of Delta variant circulation had a more severe lung involvement compared to patients in infected when Alpha variant was predominant. Despite imaging pattern seems to be not influenced by viral variant and other clinical variables, the consolidative pattern was observed more frequently in pregnancy.