基于cf-DNA与T淋巴细胞亚群的老年重症病毒性肺炎预后分层模型的构建OA

Objective To investigate factors influencing in-hospital mortality in elderly patients with severe viral pneumonia,and to construct and validate a nomogram prediction model integrating plasma cell-free DNA(cf-DNA),peripheral blood T lymphocyte subsets(CD3+,CD4+and CD8+T lymphocyte percentages),and clinical indicators.Methods A total of 229 elderly patients with severe viral pneumonia admitted to the hospi-tal from January 2022 to June 2025 were selected as study subjects.At enrollment,plasma cf-DNA and periph-eral blood T lymphocyte subsets(CD3+,CD4+,and CD8+T lymphocyte percentages)were measured.Clinical outcomes were followed up,and the patients were divided into a death group and a survival group according to survival status.Stepwise multivariate Logistic regression analysis was used to identify factors influencing in-hospital mortality in elderly patients with severe viral pneumonia.Based on the regression analysis results,a nomogram prediction model was constructed.Receiver operating characteristic(ROC)curve analysis,calibra-tion curve analysis,and decision curve analysis were used to evaluate model performance,and internal valida-tion was performed using the bootstrap resampling method.Results Among the 229 patients,61 died during hospitalization,yielding a mortality rate of 26.64%.Plasma cf-DNA level and peripheral blood CD8+T lym-phocyte percentage were significantly higher in the death group than those in the survival group(P<0.05),whereas CD3+and CD4+T lymphocyte percentages were significantly lower in the death group than those in the survival group(P<0.05).Multivariate Logistic regression analysis showed that elevated cf-DNA level,age≥75 years,complicated by respiratory failure and multiple organ dysfunction were risk factors for in-hos-pital mortality in elderly patients with severe viral pneumonia(P<0.05),whereas elevated CD3+T lympho-cyte percentage was a protective factor for in-hospital mortality in elderly patients with severe viral pneumonia(P<0.05).Based on the regression results,a prediction model was constructed.The Hosmer-Lemeshow test of this model yielded χ2=6.672 and P>0.05,indicating good model fit.ROC curve analysis showed that the area under the curve of the model for predicting in-hospital mortality was 0.889(95%CI:0.854-0.924).The calibration curve demonstrated good consistency between the predicted and observed probabilities,with a mean absolute error of 0.005.Decision curve analysis indicated that the model provided clinical net benefit within a certain threshold probability range.Conclusion In elderly patients with severe viral pneumonia who died dur-ing hospitalization,plasma cf-DNA level is elevated and peripheral blood CD3+and CD4+T lymphocyte per-centages are decreased.The prediction model constructed based on cf-DNA,CD3+T lymphocyte percentage and clinical indicators demonstrates good discrimination and calibration,and may provide a reference for in-hospital mortality risk stratification.