Technique and interpretation of the Weil-Felix test in typhus fever

Abstract
Two different types of the curve of OX19 agglutinin formation are found in patients suffering from louse-borne typhus. The two types of reaction curve are related to the clinical course of the disease and form the basis for the interpretation of the results of the Weil-Felix test. Rickettsial vaccines stimulate demonstrable OX19 agglutinins in a relatively high proportion of inoculated persons. The OX19 antibody response is of a moderate degree, similar to the O antibody response after T.A.B. inoculation. Residual OX19 agglutinins, due to a previous attack of louse-borne typhus, do not show significant fluctuation of the titre in the course of various febrile diseases. It may be assumed that the same holds for OX19 agglutinins produced in response to anti-typhus inoculation. Residual O agglutinins for typhoid and paratyphoid bacilli, whether due to previous infection or inoculation, also behave in like manner. The technique of the agglutination test with preserved suspensions of Proteus OX19 is described. Repeated tests with low dilutions of serum, including dilutions 1 : 25 and 1 : 50, are of especial importance in early diagnosis. Some of the possible sources of error are discussed. The various modifications of a slide-agglutination test, now used by German workers for rapid diagnosis in field conditions, are briefly mentioned. The following typhus-like fevers occur in the areas which at present are, or soon may become, a theatre of operations, viz. , murine typhus, “fièvre boutonneuse,” tick typhus of India and scrub typhus. The Proteus OX reactions peculiar to each of these varieties of the disease are compared with the OX19 reaction as it is known in louse-borne typhus.