Amino-terminal natriuretic peptide precursor is a blood test used to determine whether a patient is currently in heart failure, as well as the severity of heart failure and the prognosis of patients with heart failure. This indicator is affected by many factors, such as age, renal insufficiency, inflammation and infection, and tumors, all of which may lead to an increase in this indicator. Therefore, this index should be evaluated in conjunction with a cardiac ultrasound of the left ventricular ejection fraction. If the patient is currently younger than 50 years of age, a relative value of >450ng/L is relevant. If the patient is currently 50-75 years of age, then a value greater than 900ng/L is highly relevant to consider the presence of heart failure. If the patient is currently older than 75 years of age, a corresponding value greater than 1800 ng/L would represent the presence of heart failure.