Comparison of the Laughlen Reaction for Syphilis with the Wassermann and Kahn Reactions.

In 1935 Laughlen described a rapid agglutination test for syphilis using an alcoholic antigen prepared in a way similar to that of the ordinary Kahn antigen but modified by the addition of a fat stain and of compound tincture of benzoin. For use it was diluted with 1-5 per cent saline. The sensitivity was adjusted by means of an electrolyte. This antigen was active for about three weeks if kept at room temperature in the dark, in hard glass containers. Since then several modifications have appeared-one by Laughlen in 1938, another by Walters in 1939, and a third by Tulloch (unpublished). An investigation of the reaction was begun in 1938 but it had to be abandoned at the beginning of the war and an opportunity for continuing this work has only recently presented itself. Through the courtesy of Professor W. J. Tulloch details of his modification have been obtained. Antigen prepared by his method proved satisfactory, but difficulty was experienced with some batches owing to oversensitivity and the saline antigen could not be kept effective for longer than about three weeks. To overcome these difficulties the use of buffered saline was tried. Buffering at pH 7'2 proved to be most satisfactory. In addition, in the tests described, Army Presumptive Kahn antigen has been used instead of ordinary Army Kahn Antigen because it seemed to produce a more stable antigen without much alteration in its sensitivity.