858 



THE KAHN REACTION 



reacting units according to the formula S = 4D, where 5 is the serum potency in terms of re- 

 acting units and D is the maximum dilution of serum giving a positive reaction. 



Clinical application: To determine the relative intensity of syphilitic reacting sub- 

 stances in the blood, especially in the cases of patients receiving anti-syphilitic therapy. 



Presumptive procedure with scrum. — This is a qualitative one-tube test consisting of 

 0.15 cc. of serum with o.oi cc. of antigen suspension, employing special antigen — a some- 

 what more sensitive antigen than standard. The results are interpreted on the basis of posi- 

 tive or negative, depending on the presence or absence of a definite precipitate. 



TABLE I 



Outline of Kahn Test and Interpretation of Results 



Clinical application: Aid in diagnosis of obscure cases where the routine test might be 

 negative ; check on treated cases. 



Qualitative spinal fluid procedure. — This method requires precipitating the globulins in 

 spinal fluid with saturated ammonium sulphate solution, producing 40 per cent saturation, 

 separating the globulins by centrifugation, and redissolving them in an amount of normal 

 saline equal to one-tenth of the original amount of spinal fluid. The dissolved globulin, in a 

 0.15-CC. amount, is now added to o.oi cc. of antigen suspension and the test completed in the 

 usual manner. The results are interpreted on a plus sign basis. 



Clinical application: In the diagnosis of neurosyphilis and check on treatment. 



Quantitative spinal fluid procedure.^ — This is a continuation of the qualitative procedure, 



' Lederer, A. {U. S. Vet. Bur. M. Bull. 3, p. 52. 1926) proposed a combined qualitative and quan- 

 titative spinal-fluid procedure. 



