Rarer quantitative and qualitative abnormalities of coagulation

The rare clotting defects described here constitute important clinical and laboratory entities. They are not as rare as originally thought, and may be encountered in every laboratory. By now every coagulation laboratory has had the chance of seeing an uncommon coagulation deficiency and abnormality. During the past 17 years we have seen a large number of these patients. This is surely not representative of the real incidence of these disorders, since we act as a reference laboratory for a large area with a population of about 10 million people. The suspicion of an abnormality should arise every time results of routine clotting tests are not fully explicable on the basis of accepted knowledge. The concomitant use of clotting, chromogenic and immunological assays should be carried out in every suspected case. Discrepancies among these results over 15% may be indicative of an abnormality. For example, every factor VII defect should be evaluated using thromboplastins of a different origin in order to rule out dysproconvertinaemias. Prolonged thrombin times should also be carefully evaluated using other thrombin-like reagents. The major features of congenital disorders are: the fixity of the defect, in the sense that the pathological tests do not vary significantly with time, and the frequent occurrence of similar or milder clotting alterations in family members. These congenital clotting disorders have contributed considerably to the understanding of the the clotting mechanism. This, in turn, has benefited several patients in general.