A diagnostic method for determining prognosis of a myocardial infarcted patient, wherein the amounts of FXIII protein are determined on the day of myocardial infarction (t0) and at least on the following three days (t1 to t3), wherein a lowering of FXIII amount on any one of t0 to t3 below a threshold value is indicative of an increased risk of poor prognosis.
