On the clinical significance of acquired antithrombin deficiency.

The concentration of antithrombin III (AT) was determined with a chromogenic method in plasma samples from 1,302 patients referred for evaluation of the haemostatic system. A clearly subnormal AT level (below 60%) was found in 129 patients. In ten cases, this was explained by known (8 cases) or suspected (2 newborns) hereditary deficiency. Only in 5% of the 600 cases referred with definite or suspected thrombosis, AT was below 60%. These cases had a lethality of about 20%. In about 30% of the cases with liver disease, AT was below 60%. In a group of 72 patients with either severe infection, cardiac insufficiency, malignancy or suspected DIC for other reasons, AT was below 60%. Also in this group lethality was about 50% despite lack of a clear DIC blood profile in 67 of the 72 patients. The results indicate that an AT value below 60% of normal, unexplained by hereditary deficiency, carries a grave prognosis.