Precipitation Test for Syphilis 



331 



forming a milky, opalescent mixture with no trace of a precipi- 

 tate. This mixture is then ready for use. 



The Test: Three-tenths c.c. of serum, previously inactivated 

 for one-half hour at 56° C, is measured into a small tube and 



0. 05 c.c. of new antigen mixture added to it. The tube is shaken 

 for about a minute. Practically all tubes will become slightly 

 cloudy but those showing spontaneous reactions will show def- 

 inite precipitations in clear serums. The final reading in this 

 case also is taken after overnight incubation at 37° C. 



The Reading of Results 

 The results are read in accordance with the following scale : 



1. One or more large clumps = H — I — I — h 



2. Large sized flocculi = H — | — h 



3. Moderate sized flocculi or granules = H — h 



4. Small flocculi or granules == +. 



5. Very small flocculi or granules = ±. 



It is recommended in reading the results that all tubes showing 

 the presence of definite clumps or heavy precipitates in both pro- 

 cedures be first picked out and set aside in a special rack. 

 These are the definitely positive reactions (H — | — | — h and 

 H — I — h) and can be read with very little difficulty. The remain- 

 ing tests carried out with Procedure I are read as follows : 



1. Slant the tube to such an extent that it is alrnost horizontal. 

 This causes the fluid to spread into a thin layer. 2. Hold the 

 slanted tube some inches above the level of the eyes. 3. Focus 

 against some dark object such as the lower part of a window 

 shade. 4. Observe whether the thin layer of fluid is entirely clear 

 or has fine particles evenly distributed. 



All remaining tubes of Procedure II receive one c.c. of salt 

 solution each and rack is gently shaken and permitted to stand 

 about ten minutes. The negative tests show opalescence while 

 the positive tests show the presence of precipitates. With some 

 antigens this procedure is unusually sensitive and doubtful (±) 

 reactions may safely be considered negative. Salt solution may 

 occasionally be used with advantage also in diluting some tests 

 carried out with Procedure I. 



The results of the two methods outlined check very closely. 

 In isolated cases where there is disagreement, the average finding 

 of the two methods is taken as the final result. 



