A Rapid Precipitation Test for Syphilis

Ingredients: This test unlike the other existing precipitation tests for syphilis requires no dilution of the serum and antigen either before or after mixing them. Therefore the test is dealing with only two ingredients: serum and antigen.

Serum: The serum is obtained and inactivated in the usual way. As only small amounts of serum are needed it may be sufficient to secure the blood from the finger.

Antigen: Since the work of Sachs 1 in 1911, it has been a well established fact that the addition of cholesterin to the alcoholic beef heart antigen increases the sensitiveness of the latter in complement fixation and precipitation tests for syphilis. The solubility of cholesterin in alcohol is limited and therefore the cholesterin content in the alcoholic antigen cannot go beyond a certain degree (about 0.8%). It was thought that by using better solvents it would be possible to increase the cholesterin content of antigen. After several experiments acetone (at 37°) was found to be satisfactory for that purpose and the antigen was prepared by adding 2% solution of cholesterin in acetone to an equal volume of alcoholic beef heart extract. This extract is obtained by adding 5 cc. of alcohol (95%) for every gram of beef heart muscle powder from which the ether soluble substances were previously removed by ether extraction. The principle of preliminary ether extraction introduced by Neyman and Gager 2 and adopted by Kahn, 3 Meinicke, 4 et al., was found to be of advantage also in this test. It is advisable to keep in stock separately the alcoholic extract and cholesterin solution and to prepare mixtures sufficient for only one week's need. If cholesterin crystals precipitate out the solution is placed in an incubator at 37° in order to dissolve them.