ABSTRACT
Background The outbreak of COVID-19 in Xi'an between 2021 and 2022 was a large-scale local epidemic in a large city with a huge number of cases. It is necessary to analyze and summarize the contents of this outbreak. Objective To analyze the disease characteristics of patients with COVID-19，and to explore the risk factors as well as predictors of serious cases. Methods General data and laboratory parameters were retrospectively collected from patients diagnosed with a new coronavirus pneumonia who were admitted to the Fourth People's Hospital of Xi'an between December 2021 and January 2022. Based on the the ratios of total IgG to lymphocyte percentage （IgG∶L%），total IgM to lymphocyte percentage （IgM∶L%），total IgG to lymphocyte count ratio （IgG∶L#），and total IgM to lymphocyte count ratio （IgM∶L#），patients were divided into three groups: mild and common，severe and critical. Multivariate Logistic regression analysis was used to explore the risk factors of developing severe and critically new coronavirus；then the ROC curve was drawn to analyze the predictive indexes and predictive value of severe and critical COVID-19，the area under the ROC curve （AUC） was calculated，and the AUC of each index was compared using the Delong test. Results A total of 699 patients with identified COVID-19 were finally included，and divided into two groups: the mild and common（n=678） and the severe and critical （n=21） forms，with the mild and common forms having younger age，and less underlying disease，D-dimer，IgM ∶ L%，IgM ∶ L#，and higher lymphocyte percentage and lymphocyte count than the severe and critical forms （P<0.05）. Multivariate Logistic regression analysis showed that age〔OR=1.068，95%CI（1.031，1.105），P<0.001〕，D-dimer 〔OR=1.612，95%CI（1.026，2.533），P=0.038〕as well as IgM ∶L#〔OR=1.034，95%CI（1.006，1.063），P=0.018〕 were risk factors for the development of severe and dangerous new coronavirus，and lymphocyte percentage 〔OR=0.918，95%CI（0.844，0.997），P=0.043〕was a protective factor for the development of severe and critical new coronavirus. To establish a joint prediction model for severe and critical novel coronavirus infection，P=-5.031+0.065×age-0.086× lymphocyte percentage +0.738× lymphocyte count +0.477× D-dimer +0.034×IgM∶L#，and the cutoff value for combined detection to predict severe and critical COVID-19 was 0.04，with a sensitivity of 90.00%，a specificity of 83.18%，and its AUC of 0.912〔95%CI（0.858，0.965）〕，which was greater than that for age （Z=5.314，P<0.001），lymphocyte percentage （Z=-1.987，P=0.047），D-dimer （Z=2.273，P=0.023），and IgM∶L# （Z=0.161，P<0.001），with statistically significant differences. Conclusion In the acute phase of COVID-19，there is an imbalance between inflammatory response and cellular immune function，and this imbalance，along with age and D-dimer，are all risk factors for severe COVID-19. Combined indicators including age，D-dimer，lymphocyte percentage and IgM∶L# can effectively predict severe and critical COVID-19. © 2023 Chinese General Practice. All rights reserved.