Objective: To assess the significance of elevated serum N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in predicting 30-day mortality rate for patients in intensive care unit (ICU).
Methods: A retrospective study was conducted. The clinical data of 480 patients admitted to ICU in Tianjin First Center Hospital from June 2012 to October 2013 were studied. The characteristics of patients were recorded, the acute physiology and chronic health evaluationII ( APACHEII) score was calculated, and the routine blood tests, blood biochemistry, and serum NT-proBNP level within 24 hours after admission were determined. Patients were divided into non-survival and survival groups according to 30-day outcome, and the characteristics and clinical parameters were compared between two groups, and single factor analysis affecting prognosis was analyzed. All patients were divided into four groups according to four percentile method as NT-proBNP<280 ng/L (group Q1), 280 ng/L≤NT-proBNP<1 200 ng/L (group Q2), 1 200 ng/L≤NT-proBNP<1 990 ng/L (group Q3), 1 990 ng/L≤NT-proBNP<4 700 ng/L (group Q4). A Cox regression analysis was used to test the independence of the predictors. A receiver operator characteristic curve (ROC curve) was plotted to compare the power of APACHEII score and NT-proBNP in predicting the outcome. Kaplan-Meier analysis was used to assess survival rate among different NT-proBNP patients.
Results: By single factor analysis it was shown that age, APACHEII score, creatinine, NT-proBNP and severe infection were those influencing the outcome. NT-proBNP 1 200-4 700 ng/L (groups Q3 and Q4) and APACHEII score>20 were independent risk factors for predicting outcome [relative risk (RR) for group Q3 was 3.624, 95% credibility interval (95%CI) was 1.258-10.138; RR for group Q4 was 5.059, 95%CI was 3.202-9.993; RR for APACHEII score>20 was 2.987, 95%CI was 1.345-5.823]. The area under the ROC curve (AUC) for APACHEII score and serum NT-proBNP was similar, and it was 0.831 (95%CI 0.778-0.884) and 0.876 (95%CI 0.827-0.925), respectively. The cut-off value of NT-proBNP for predicting mortality was 1 250 ng/L. Kaplan-Meier analysis showed that groups of Q2, Q3 and Q4 had lower cumulative survival rate compared with group Q1 (26.5%, 25.4%, 16.2% vs. 29.6%), and group Q4 showed most significant extent of lowering of survival rate (χ(2)=122.920, P<0.05).
Conclusions: Elevated NT-proBNP level in ICU patients signify severity of the disease, and it is an independent predictor of death of ICU patients.