The cardiolipin-lecithin test for syphilis.

as the antigen for a simplified precipitation test for syphilis. Cardiolipin is the lipid which, in combination with lecithin, gives the alcoholic extract of beef heart its antigenic properties. It is a complex phosphatidic acid with a molecular weight of 2195 and iodine number 120-125. It requires lecithin and cholesterol for antigenicity. It has not yet been synthesized. The cardiolipin-lecithin antigen may be adjusted to any desired sensitivity, within limits, merely by altering the ratio of cardiolipin and lecithin. Kline (1947) recommended a cardiolipin-lecithin ratio of 1: 9 4 and 1: 10 6. Our attempts to isolate and prepare the pure cardiolipin from beef heart were not successful. We have used as our antigen a cardiolipin-lecithin mixture of 1 : 10, standardized by Dr. Kline and supplied by the La Motte Chemical Company. The cardiolipin-lecithin (C.L.) test is now done as