Background: Corona virus disease (COVID-19) is an infectious respiratory disease that has spread rapidly across the world. Many studies have already evaluated the clinical features of COVID-19, but how it compares with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative community-acquired pneumonia (SN-CAP) is still unclear. Moreover, COVID-19 mortality is correlated with disease severity, but indicators for severity grading have not been specified. We aimed to analyze the clinical characteristics of COVID-19 in comparison with SN-CAP and find indicators for disease severity in COVID-19.

Methods: Patients diagnosed with COVID-19 and SN-CAP were enrolled. Clinical, radiological, and laboratory data were analyzed.

Results: The numbers of COVID-19 and SN-CAP patients enrolled were 304 and 138, respectively. The age of the patients was not significantly different between the groups. Compared with SN-CAP, COVID-19 patients had more symptoms of fever and dyspnea; and showed significant difference in blood count results. Computed tomography (CT) imaging of COVID-19 patients showed patchy ground-glass opacities that correlated with disease severity, whereas the CT imaging of SN-CAP patients showed patchy high-density shadows. COVID-19 patients were classified into moderate, severe, and critically severe groups. The severe and critically severe groups had elevated levels of white blood cells (WBC), neutrophils, platelets, C-reaction protein (CRP), lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), troponin-I, creatinine, and blood urea nitrogen (BUN). However, they had decreased levels of lymphocytes, lymphocyte ratio, and albumin. Compared with the younger patients, the older COVID-19 individuals had more chronic diseases and significantly elevated levels of WBC, neutrophil, and CRP levels.

Conclusion: SN-CAP showed more inflammatory reaction than COVID-19. Old people with chronic diseases are more susceptible to COVID-19 and have a high likelihood of developing severe and critically severe infection. Levels of WBC, lymphocytes, neutrophils, CRP, NLR, PLR, troponin-I, creatinine, and BUN are important indicators for severity grading in COVID-19.

背景：冠状病毒病（COVID-19）是一种传染性呼吸道疾病，已在世界范围内迅速传播。许多研究已经评估了 COVID-19 的临床特征，但其与严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 阴性社区获得性肺炎 (SN-CAP) 的比较仍不清楚。此外，COVID-19死亡率与疾病严重程度相关，但严重程度分级指标尚未明确。我们的目的是与 SN-CAP 进行比较，分析 COVID-19 的临床特征，并找到 COVID-19 疾病严重程度的指标。

方法：诊断患有 COVID-19 和 SN-CAP 的患者被纳入。分析临床、放射学和实验室数据。

结果：入组的 COVID-19 和 SN-CAP 患者人数分别为 304 例和 138 例。各组之间患者的年龄没有显着差异。与SN-CAP相比，COVID-19患者出现更多发热、呼吸困难症状；且血细胞计数结果显示出显着差异。 COVID-19 患者的计算机断层扫描 (CT) 成像显示与疾病严重程度相关的斑片状毛玻璃混浊，而 SN-CAP 患者的 CT 成像显示斑片状高密度阴影。 COVID-19患者被分为中度、重度和重症组。重症组和危重症组白细胞（WBC）、中性粒细胞、血小板、C反应蛋白（CRP）、淋巴细胞比值（NLR）、血小板与淋巴细胞比值（PLR）、肌钙蛋白-I、肌酐和肌酐水平升高。血尿素氮（BUN）。然而，它们的淋巴细胞水平、淋巴细胞比率和白蛋白水平下降。与年轻患者相比，老年 COVID-19 患者患有更多慢性病，且 WBC、中性粒细胞和 CRP 水平显着升高。

结论： SN-CAP 比 COVID-19 显示出更多的炎症反应。患有慢性病的老年人更容易感染COVID-19，并且很有可能发展为重症和危重症感染。 WBC、淋巴细胞、中性粒细胞、CRP、NLR、PLR、肌钙蛋白-I、肌酐和 BUN 的水平是 COVID-19 严重程度分级的重要指标。