An in vitro method for diagnosing a disease accompanied by or related to necrotic processes in a subject comprising: • determining the activity of DPP 3 in a sample of bodily fluid of said subject, wherein DPP 3 activity is measured by addition of the fluorogenic substrate ARG-ARG-βNA and monitoring fluorescence in real time • comparing said activity to a predetermined threshold, • wherein said subject is diagnosed as having a disease accompanied by or related to necrotic processes if said determined activity is above said predetermined threshold, wherein necrotic processes are processes that lead to death of cells and release of DPP 3 from the cells into said bodily fluid, and wherein the activity of DPP 3 is determined by an in vitro method of determining active DPP 3 in said bodily fluid sample of a subject comprising the steps: • Contacting said sample with a capture-binder that binds specifically to full-length DPP 3, wherein said capture binder is immobilized on a surface, • Separating DPP 3 bound to said capture binder, wherein said separation step is a washing step that removes ingredients of the sample that are not bound to said capture-binder from the captured DPP 3, • Adding the substrate of DPP 3 to said separated DPP 3, • Quantifying DPP 3 activity by measuring the conversion of the substrate of DPP 3, wherein the binding region of DPP 3 for the capture-binder is not within the region of amino acids 316- 669 of SEQ ID No. 1, wherein said sample is a blood sample which is plasma, and wherein said predetermined threshold is between 0.5 and 2 nmol β NA min -1 ml -1 and wherein said predetermined threshold divides between healthy and diseased subjects and wherein said disease is selected from the group comprising: acute heart failure, sepsis, acute kidney injury, lower respiratory tract infection, acute myocardial infarction, cardiogenic shock, septic shock and liver failure. • determining the activity of DPP 3 in a sample of bodily fluid of said subject, wherein DPP 3 activity is measured by addition of the fluorogenic substrate ARG-ARG-βNA and monitoring fluorescence in real time • comparing said activity to a predetermined threshold, • wherein said subject is diagnosed as having a disease accompanied by or related to necrotic processes if said determined activity is above said predetermined threshold, wherein necrotic processes are processes that lead to death of cells and release of DPP 3 from the cells into said bodily fluid, and wherein the activity of DPP 3 is determined by an in vitro method of determining active DPP 3 in said bodily fluid sample of a subject comprising the steps: • Contacting said sample with a capture-binder that binds specifically to full-length DPP 3, wherein said capture binder is immobilized on a surface, • Separating DPP 3 bound to said capture binder, wherein said separation step is a washing step that removes ingredients of the sample that are not bound to said capture-binder from the captured DPP 3, • Adding the substrate of DPP 3 to said separated DPP 3, • Quantifying DPP 3 activity by measuring the conversion of the substrate of DPP 3, wherein the binding region of DPP 3 for the capture-binder is not within the region of amino acids 316- 669 of SEQ ID No. 1, wherein said sample is a blood sample which is plasma, and wherein said predetermined threshold is between 0.5 and 2 nmol β NA min -1 ml -1 and wherein said predetermined threshold divides between healthy and diseased subjects and wherein said disease is selected from the group comprising: acute heart failure, sepsis, acute kidney injury, lower respiratory tract infection, acute myocardial infarction, cardiogenic shock, septic shock and liver failure. wherein necrotic processes are processes that lead to death of cells and release of DPP 3 from the cells into said bodily fluid, and wherein the activity of DPP 3 is determined by an in vitro method of determining active DPP 3 in said bodily fluid sample of a subject comprising the steps: • Contacting said sample with a capture-binder that binds specifically to full-length DPP 3, wherein said capture binder is immobilized on a surface, • Separating DPP 3 bound to said capture binder, wherein said separation step is a washing step that removes ingredients of the sample that are not bound to said capture-binder from the captured DPP 3, • Adding the substrate of DPP 3 to said separated DPP 3, • Quantifying DPP 3 activity by measuring the conversion of the substrate of DPP 3, • Contacting said sample with a capture-binder that binds specifically to full-length DPP 3, wherein said capture binder is immobilized on a surface, • Separating DPP 3 bound to said capture binder, wherein said separation step is a washing step that removes ingredients of the sample that are not bound to said capture-binder from the captured DPP 3, • Adding the substrate of DPP 3 to said separated DPP 3, • Quantifying DPP 3 activity by measuring the conversion of the substrate of DPP 3, wherein the binding region of DPP 3 for the capture-binder is not within the region of amino acids 316- 669 of SEQ ID No. 1, wherein said sample is a blood sample which is plasma, and wherein said predetermined threshold is between 0.5 and 2 nmol β NA min -1 ml -1 and wherein said predetermined threshold divides between healthy and diseased subjects and wherein said disease is selected from the group comprising: acute heart failure, sepsis, acute kidney injury, lower respiratory tract infection, acute myocardial infarction, cardiogenic shock, septic shock and liver failure.