ST2 concentration is not affected by the age, sex, or BMI of the patient, it does not depend on the aetiology of heart failure or whether the patient has atrial fibrillation or anaemia, neither does it correlate with kidney function. ST2 level quickly responds to changes in the health condition of the patient, making it easier for doctors to make a decision in instances where the treatment must be started or altered immediately, or the person has to be hospitalised in time. ST2 blood concentration can predict the health condition of heart failure patients the best, select the patients at the highest risk early, and expose the necessity of re-hospitalisation and the death risk.