ObjectiveTo evaluate the value of blood urea nitrogen to creatinine ratio (UCR) in predicting the condition and prognosis of severe pneumonia patients.MethodsA total of 408 patients with severe pneumonia hospitalized in the intensive care unit (ICU) of Fangcun branch of Guangdong Provincial Hospital of traditional Chinese medicine from January 1, 2017 to August 1, 2020 were retrospectively collected. The patients were divided into a survival group (320 cases) and a death group (88 cases) according to the outcome of hospitalization. This study analyzed the relationship between UCR level and general information, condition, and treatment needs of severe pneumonia patients; and compared UCR, the value of neutrophil to lymphocyte ratio, the levels of hematocrit, C-reactive protein, procalcitonin and D-dimer, and the scores of Acute Physiology and Chronic Health EvaluationⅡ and Pneumonia Severity Index between the survival group and the death group. Receiver operating characteristic (ROC) curve was used to analyze the prognostic value of the above indicators. Logistic regression was used to analyze the risk factors of death of severe pneumonia.ResultsThe age of the patients died of severe pneumonia was higher than that of the survival patients (P<0.05); The mortality rate of severe hospital acquired pneumonia was higher than that of severe community acquired pneumonia (P<0.05); The level of UCR was higher in the patients over 70 years old (P<0.05); UCR level of the severe pneumonia patients with acute exacerbation of chronic obstructive pulmonary disease or multiple organ dysfunction syndrome during hospitalization was higher (P<0.05); The UCR level was higher in the patients with severe pneumonia whose ICU stay was more than 10 days (P<0.05); The UCR level of the severe pneumonia patients with mechanical ventilation longer than 180 hours was higher (P<0.05); UCR level of the severe pneumonia patients who died during hospitalization was higher than that of the survival group (P<0.05); The area under ROC curve of UCR for predicting death in the patients with severe pneumonia was 0.648 (95%CI 0.576 - 0.719), the cut-off value was 108.74, the sensitivity was 47.7%, and the specificity was 77.8% (P<0.05). PSI > level 3 (OR=4.297, 95%CI 2.777 - 6.651) and UCR > 108.74 (OR=0.545, 95%CI 0.332 - 0.896) were independent risk factors for death in the patients with severe pneumonia (P<0.05).ConclusionUCR has certain value in evaluating the condition and prognosis of severe pneumonia patients.