460 IMMUNOLOGY 



A strongly positive serum usually produces clumps of sufficient 

 size for macroscopic diagnosis. This leads to the omission of the 

 microscopic examination — a practice to be condemned. Weakly 

 positive reactions are easily missed when such a practice is fol- 

 lowed. 



It is also recommended that a positive and a negative serum 

 control be included in each series of tests (on each side). Anti- 

 gen (0.0070 c.c.) plus saline (0.05 c.c.) is also included in this 

 laboratory as an additional control. 



In addition to the routine diagnostic test described above, Kline 

 has an elimination test, comparable in purpose to the presumptive 

 test of Kahn. This test differs in the preparation of the antigen. 

 It is as follows : 



Distilled water 0.85 c.c. 



Cholesterol 1 per cent ab. alcohol 1.0 c.c. 



Antigen 0.1 c.c. 



yodium chloride, C.P., 0.85 per cent 2.45 c.c. 



Elimination Test. — The emulsion is prepared as for the diag- 

 nostic test. After being incubated in a water bath at 56° C. for 

 15 minutes, it is centrifuged for fifteen minutes (eighth setting 

 rheostat, centrifuge size 1, type S. B.). The supernatant fluid is 

 removed and the sides of the tube are dried with blotting paper. 

 The sediment is resuspended in 1.0 c.c. of isotonic salt solution. 

 The technique for the test is like that of the diagnostic reaction. 

 More details pertaining to the Kline tests are given in Supplement 

 No. 11. 



Use of Elimination Test. — The elimination test is useful in 

 cases in which it is desired to rule out syphilis as a possible com- 

 plication. It has been successfully used in testing blood donors, 

 in health examinations, and in routine examination of patients be- 

 ing admitted to institutions or hospitals for other than venereal 

 treatment. 



Sources of Error. — A common source of difficulty resides in the 

 cholesterol solution. To give satisfactory results, the cholesterol 

 must be weighed accurately. The error should not exceed 0.005 

 grams per gram of cholesterol. The alcohol used in preparing the 

 solution should be free from traces of water. Such alcohol will not 

 color anhydrous copper sulphate. This reagent rapidly absorbs 



