A Method for Preservation of Oxalated Plasma Clot for Fibrinolytic Tests

Oxalated plasma usually loses its ability to form a clot upon addition of calcium chloride when kept in the icebox for 72 hours.

We have been testing the fibrinolytic power of hemolytic streptococci immediately after isolation and at regular intervals thereafter to observe any changes in this property and its relation to other biological characteristics of the organism. A susceptible plasma clot from an individual was used repeatedly, necessitating a considerable number of bleedings, resulting usually in loss of time and material. For these reasons we decided to search for a method to preserve plasma while retaining its ability to clot readily and maintaining its susceptibility to lysis unaffected. This has been accomplished by the following method:

Human blood from a susceptible person was obtained and distributed in 5 cc amounts into small glass bottles, each containing 10 mg of potassium oxalate in the form of the dry powder. After mixing well by gentle shaking, the plasma was separated by centrifugation. The susceptibility of this plasma to the lytic action of hemolytic streptococci was tested, employing the original technic of Tillett and Garner. 1 ∗ A 16- to 20-hour-old culture in neopeptone broth containing 0.02% glucose to which a drop of defibrinated rabbit blood was added at the time of inoculation, was used in all the tests. Transplants were always made to this medium from the stock cultures on blood agar. From the growth thus obtained a second transplant to a tube of glucose neopeptone blood broth was made. The growth from this second transplant was actually employed in the test. Clotting took place within 10 minutes. Dissolution was complete in from 10 to 15 minutes.