INTRODUCTIONDifferentiating acute heart failure (AHF) from chronic obstructive pulmonary disease (COPD) or asthma is essential for prompt and appropriate treatment in patients presenting with acute shortness of breath in the emergency department (ED).AIMThis study aimed to evaluate the diagnostic accuracy of bedside lung ultrasound, N-terminal pro-brain natriuretic peptide (NT-proBNP) level, and clinical criteria (using the modified Boston criteria) for differentiating AHF from COPD/asthma.MATERIALS AND METHODSThis prospective cohort study was conducted in the Emergency Medicine Department of the All India Institute of Medical Sciences, Rishikesh, from June 2023 to December 2023. Patients presenting with acute shortness of breath were managed using clinical assessment (according to modified Boston criteria), lung ultrasound, and NT-proBNP measurements.RESULTSOut of 104 patients, 45 were diagnosed with AHF, and 59 had pulmonary-related causes of shortness of breath. Lung ultrasound demonstrated a sensitivity of 100%, specificity of 62.3%, negative predictive value (NPV) of 100%, and positive predictive value (PPV) of 65.15% for diagnosing heart failure. NT-proBNP, with a cutoff value of 500 pg/mL, showed 100% sensitivity, 91.8% specificity, 100% NPV, and 89.58% PPV. The Boston modified criteria had a sensitivity of 76.74%, specificity of 88.52%, NPV of 84.38%, and PPV of 82.5%. A comparison of these three diagnostic methods revealed significant differences between the ultrasound findings and both NT-proBNP and modified Boston criteria (p < 0.05). The combination of ultrasound signs and NT-proBNP yielded 100% sensitivity, specificity, NPV, and PPV.CONCLUSIONSThe integration of lung ultrasound, NT-proBNP level, and clinical criteria provides a reliable and rapid approach for differentiating AHF from COPD/asthma in the ED.