Behaviour of antithrombin III abnormalities in the crossed immunoelectrophoresis system

Antithrombin III (AT III) abnormalities can be characterized by means of crossed immunoelectrophoresis. In the past, it was thought that the abnormalities could be demonstrated only if heparin is present in the system. Now some conditions (AT III Trento, for example) are known to show an abnormal pattern only in the absence of heparin. This indicates that some of the changes are heparin-independent. Furthermore, it could be demonstrated that in some cases the abnormality is present only in serum (AT III Vicenza, for example). Therefore, the test should be carried out as a screening procedure both in plasma and serum and in the presence or absence of heparin in every case of suspected AT III abnormality.