Abstract
Prevailing methods for the determination of the fragility of erythrocytes are based upon the theory of their hemolytic stability when brought into contact with chemicals such as saponin and bile salts, with specific sera, or with hypotonic salt solutions. Theoretical as well as practical considerations have directed the development of these studies toward improving the technique for determining the resistance of the red blood cells to solutions containing different concentrations of various salts. Of the many variations in the original method of Ribierre, 1 that of Simmel, 2 or one of its modifications, 3 appears to be the best. However, the necessity of freshly prepared hypotonic salt solution of very exact concentrations, together with the labor in using the counting chamber and the necessity for setting up a control test with a known normal blood at each observation, are definite disadvantages.
We have devised a fragility test in which the difficulties mentioned are largely eliminated. The testing of the relative fragility of the patient's cells in varying dilutions of his own plasma is the essential principle introduced in this new method.
Technique. Test tubes of 20-30 cc. capacity and capable of withstanding the high speed of the centrifuge are fitted with rubber stoppers. To each is added 2 mg. of powdered heparin, an amount sufficient to prevent the clotting of 10 cc. of blood for approximately 24 hours. After weighing out this quantity a few times to visualize the approximate volume involved, the quantity of heparin added to each test tube may be estimated without disturbing the accuracy of the test. Ten cc. of blood are drawn from one of the arm veins, using a dry (not rinsed in salt solution) 10 cc. syringe and needle.
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