Abstract:

Objective To investigate the relationship between the CURB-65 score， serum interleukin-6 （IL-6） level， procalcitonin/albumin （PCT/ALB） ratio and the prognosis of patients with severe pneumonia. Methods A retrospective analysis was conducted on the clinical data of 110 patients with severe pneumonia （severe group） admitted to the Department of Respiratory and Critical Care Medicine， Huangshan City People's Hospital between June 2022 and July 2025. Simultaneously， 55 patients with mild pneumonia （mild group） were recruited. General clinical data， CURB-65 scores upon admission， serum IL-6 levels， and PCT/ALB ratio were gathered. Pearson′s method was employed to analyze the correlation between the CURB-65 score and serum IL-6 as well as the PCT/ALB ratio. Patients with severe pneumonia were classified into the low-risk group （n = 34）， intermediate-risk group （n = 53）， and high-risk group （n = 23） according to the CURB-65 score. Based on the 28-day prognosis， they were categorized into the favorable prognosis group （n = 80） and unfavorable prognosis group （n = 30）. The CURB-65 scores， serum IL-6 levels， and PCT/ALB ratios were compared among patients with different severities and prognoses. Binary logistic regression analysis was employed to identify prognostic factors， and receiver operating characteristic （ROC） curves were plotted to assess the prognostic value of the CURB-65 score， IL-6， and PCT/ALB ratio. Results Upon admission， patients in the severe group exhibited higher CURB-65 scores， serum IL-6 levels， PCT levels， and PCT/ALB ratios， but lower ALB levels compared to those in the mild group （P < 0.05）. Pearson correlation analysis indicated that in patients with severe pneumonia， serum IL-6， PCT， and PCT/ALB ratios were positively correlated with the CURB-65 score， whereas ALB was negatively correlated with the CURB-65 score （P < 0.05）. High-risk patients had higher serum IL-6 levels and PCT/ALB ratios than both low-risk and intermediate-risk patients. Moreover， significant differences were also observed between low-risk and intermediate-risk patients （P < 0.05）. At admission， the unfavourable prognosis group had higher CURB-65 scores， serum IL-6 levels， and PCT/ALB ratios but lower ALB levels than the favourable prognosis group （P < 0.05）. Binary logistic regression analysis revealed that the CURB-65 score， serum IL-6 level， and PCT/ALB ratio were independent risk factors for the prognosis of patients with severe pneumonia （P < 0.05）. ROC curve analysis indicated that the area under the curve （AUC） of the combination of the CURB-65 score， serum IL-6 level， and PCT/ALB ratio for predicting death in severe pneumonia was 0.944 （95%CI： 0.878 - 0.980）， which was greater than that of each individual indicator （Z = 2.162， 6.931， 2.168； P < 0.05）. The sensitivity and specificity of the joint prediction were 92.59% and 95.77%， respectively. The cut-off values of the CURB-65 score， serum IL-6 level， and PCT/ALB ratio were 4， 26.45 pg/mL， and 0.79， respectively. Conclusions An elevated CURB-65 score， serum IL-6 level， and PCT/ALB ratio are all associated with the severity and poor prognosis of severe pneumonia. The combination of these three indicators holds predictive value for the prognosis and can be employed to screen high-risk patients， thus facilitating timely intervention and enhancing the prognosis.

Key words: CURB-65 score, IL-6, PCT/ALB ratio, severe pneumonia, prognosis, relationship