Ramon flocculation test for determining potency of antiscarlatinal serum.

Abstract

The Ramon flocculation test has proven quite successful for determining the potency of antitoxic diphtheria serums. It is used now at the Research Laboratory of the City Health Department for the routine study of the progress of diphtheria horses; these tests need to be verified only here and there by guinea pig inoculations.

The above results with anti-diphtheritic serums led to attempts to apply the flocculation test, if possible, for determining the potency of antiscarlatinal serums, as compared with clinical neutralization tests.

For titration of the anti-scarlatinal serum, or of toxin, we rely on skin reactions. The strength of the toxin is expressed by the number of skin doses per cc. required for a reaction; and the potency of the serum is estimated by the amount of serum required to neutralize the number of skin doses per cc. Thus if the titrated toxin contains 40,000 skin doses per cc. and flocculation occurs with 2 cc. of the tested serum, we would estimate that the serum contains 20,000 neutralizing skin doses per cc. A table can be then constructed, with a titrated toxin, in the same manner as for the diphtheria Ramon tests, on the basis of units. Thus in the above cited case the serum contains 1/2 unit per cc.; if one cc. of serum were required for neutralization, the serum would contain 1 unit; if 1/2 cc. is used, 2 units, etc.

Though the flocculation tests for scarlet fever serum were undertaken many months ago, no visible results were obtained until lately. The explanation is possible, that though we had good toxins, we did not have strong enough serums to make the test workable in the test tube. At (present our own horses as well as the horses from different laboratories have furnished us with stronger serums, and the potency of some of them can be demonstrated by flocculation test, and compared with the skin neutralization tests in humans.