Role of N-Terminal Pro B-Type Natriuretic Peptide (NT-proBNP) for Diagnosing Underlying Cardiac and Extra-cardiac Diseases in Patients presenting with Acute Breathlessness in the Emergency Department

Background: Utility of NT-proBNP in patients presenting with acute breathlessness in the Emergency Department (ED) is high. Aim and Objectives: To evaluate the role of NT-proBNP for early diagnosis of underlying cardiac and extra-cardiac diseases (renal, sepsis and respiratory failure) for patients presenting with acute breathlessness in the ED. The primary objective was correlation of NT-proBNP for diagnosing underlying diseases and the secondary objective was to establish its cutoff value to diagnose underlying diagnosis. Methods: A prospective observational study was conducted on 241 patients with acute breathlessness in ED. They were categorised into two groups based on NT-proBNP values: Group 1 (high) and Group 2 (normal) as per their age-related pre-determined cut-offs. Correlation in terms of validity of NT-proBNP against underlying diagnosis and its diagnostic values were assessed. To estimate the cut-off value of NT-proBNP for underlying diseases, Receiver Operating Characteristics (ROC) curve was plotted. Results: For underlying cardiac diseases, the cutoff value of NT-proBNP in ROC curve was 931.5 pg/ml (Sensitivity: 92.6%, Specificity: 68.0%, AUCs: 0.85, p < 0.001) and for renal diseases, the cutoff value of NT-proBNP was 2280 pg/ml (Sensitivity: 92.2%, Specificity: 76.1%, AUCs: 0.94, p < 0.001). Conclusion: This study established the role of NT-proBNP in indicating cardiac and renal involvement in patients presenting with acute breathlessness in the ED. In addition, normal NT-proBNP values rules out underlying cardiac and renal involvement. Also, higher NT-proBNP levels are indicative of multi-system involvement.