The prognostic value of serum albumin levels and respiratory rate for community-acquired pneumonia: A prospective, multi-center study

Abstract

Community-acquired pneumonia (CAP) is a respiratory disease frequently requiring hospital admission, and a significant cause of death worldwide. This study aimed to investigate the prognostic value of clinical indicators. A prospective, multi-center study was conducted (January 2017-December 2018) where patient demographic and clinical data were recorded (N = 366). The 30-day mortality rate was 5.46%. Cox Regression analyses showed that serum albumin (ALB) and respiratory rate (RR) were independent prognostic variables for 30-day survival in patients with CAP. Albumin negatively correlated with the Pneumonia Severity Index (PSI) and CURB-65 scores using Pearson and Spearman tests. Survival curves showed that a RR >24 breaths/min or ALB ≤30 g/L were associated with a significantly higher risk of mortality. The area-under-the-curve (AUC) for predicting 30-day mortality in patients with CAP was 0.762, 0.763, 0.790, and 0.784 for ALB, RR, PSI, and CURB-65, respectively. The AUC for the prediction of 30-day mortality using ALB combined with PSI, CURB-65 scores, and RR was 0.822 (95% CI 0.731-0.912), 0.847 (95% CI 0.755-0.938), and 0.847 (95% CI 0.738-0.955), respectively. Albumin and RR were found to be reliable prognostic factors for CAP. This combination showed equal predictive value when compared to adding ALB assessment to PSI and CURB-65 scores, which could improve their prognostic accuracy.

Fig 1. Correlation of serum ALB levels with two scoring systems and RR across 366 patients with CAP.

R is the correlation coefficient. Fig 1A, 1B and 1C: Levels of ALB were negatively correlated with PSI, CURB-65, and RR. ALB, serum albumin; RR, respiratory rate.

Fig 2. Kaplan–Meier analysis of 30-day mortality in patients with CAP.

Analysis was stratified by serum ALB (A) and RR (B) levels. ALB, serum albumin; RR, respiratory rate.

Fig 3. Receiver operating characteristic curve (ROC) analysis of various parameters in predicting CAP prognosis.

AUC, area-under-the-curve; ALB, serum albumin; RR, respiratory rate; PSI, Pneumonia Severity Index Score; CURB-65, confusion, urea >7 mmol/L, respiratory rate ≥30 breaths/min, low blood pressure and age ≥65 years.