We demonstrated that there was a significant relationship between the severity measured using the A-DROP scoring system and the mortality rate in patients with COVID-19 community-acquired pneumonia (CAP) in the ancestral strain, Alpha variant, and Delta variant. We investigated the usefulness of the A-DROP scoring system in SARS-CoV-2 Omicron variant CAP and compared it with severity scores, the Pneumonia Severity Index (PSI) and CURB-65 score.

We analyzed a total of 547 patients with COVID-19 CAP Omicron variant; 198 cases were the BA.1 subvariant, 127 cases were the BA.2 subvariant, and 222 cases were the BA.5 subvariant, respectively.

The mortality rates in patients with COVID-19 CAP among the three Omicron subvariants were identical in each pneumonia severity group. The mortality rate in patients with the Omicron variant was 0 % in patients classified with mild disease, 0.6 % in those with moderate disease, 10.4 % in those with severe disease, and 34.8 % in those with extremely severe disease. The mortality rate in patients with COVID-19 CAP increased depending on the severity classified according to the A-DROP system in each of the Omicron subvariants (Cochran–Armitage trend test; p < 0.001). The values of the area under the curve in Receiver Operating Characteristic analysis for prediction of 30-day mortality was 0.881, 0.879, and 0.863 for A-DROP, PSI, and CURB-65, respectively. There were no significant differences in the predictive ability of each pneumonia severity score.

Our results demonstrated that the A-DROP scoring system is useful for predicting mortality in patients with COVID-19 CAP.