Studies on the Antistreptolysin Test.

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Abstract
Summary For the assay of the degree of hemolysis in the antistreptolysin test reading at 5,250 Å was selected since the extinction values at this wave length were found constant during incubation as well as for at least one hour after. Standardized suspensions of human erythrocytes (from one donor) were used. The storage time of the blood could vary from 3 to 9 days without any appreciable change in the resistance to the hemolytic action of streptolysin. In the antistreptolysin test described it was found sufficient to determine the combining unit once for each batch of streptolysin and once for each source of erythrocytes. When calculating the 50 per cent end point the degree of hemolysis was expressed as probit. The ratio between the probit and the serum concentration was found to be linear only within certain limits. These limits must be determined for each batch of streptolysin. When repeated determinations on different occasions of the 50 per cent end point were performed, the standard deviation was 3—5.5 per cent of the mean value.