Kahn Develops a Modified Syphilis Test

Reuben Leon Kahn’s development of a simplified test for detection of the venereal disease syphilis made better control of syphilis possible and also led eventually to Kahn’s development of the universal serologic test, an advance in immunology.

Summary of Event

Syphilis is one of the chief venereal diseases, a group of diseases whose name derives from that of Venus, the Roman goddess of love. The term “venereal” arose from the idea that the diseases were transmitted solely through sexual contact with infected individuals. Although syphilis is almost always contracted in this way, it occasionally arises after contact with objects used by syphilis-infected people in highly unhygienic surroundings, particularly in the underdeveloped countries of the world. Syphilis;testing
Medicine;syphilis treatment
[kw]Kahn Develops a Modified Syphilis Test (1923)
[kw]Syphilis Test, Kahn Develops a Modified (1923)
Medicine;syphilis treatment
[g]United States;1923: Kahn Develops a Modified Syphilis Test[05730]
[c]Health and medicine;1923: Kahn Develops a Modified Syphilis Test[05730]
Kahn, Reuben Leon
Wassermann, August von

Many believe that syphilis was first introduced in Europe by the members of Christopher Columbus’s crew, supposedly after they were infected by sexual contact with West Indian women during their voyages of exploration. Columbus is reported to have died of heart and brain problems very similar to symptoms produced by advanced syphilis. According to many historians, syphilis spread rapidly throughout sixteenth century Europe.

New diseases are always devastating, partly because of lack of immunity, and early syphilis was no exception. Regrettably, the limited medicine of the time was of little help, and the early death rate from the disease was high. Every country blamed the high incidence of syphilis on some other nation (for example, the French called syphilis the Spanish disease, and vice versa). It was not until 1530 that the Italian physician and poet Fracastor coined the name “syphilis” in an epic poem.

The origin of syphilis in the Western Hemisphere is supported by the reported paleontological evidence of its existence in pre-Columbian skeletons throughout North, South, and Central America. In contrast, no such evidence has been obtained—according to proponents of this theory—in the pre-Columbian remains found in Europe or Asia. Another group of researchers has argued that this theory of the origin of syphilis is not correct, and controversy over the issue continues in the twenty-first century.

Modern syphilis is much milder than the original disease, and relatively uncommon, but if it is not identified and treated appropriately, it can be devastating and even fatal. When syphilis is passed from a pregnant woman to her unborn child, the results are often serious health problems for the child that can include paralysis, insanity, and heart disease. Given the potential negative effects of the disease, the detection and cure of syphilis are important worldwide.

Syphilis is caused by a spiral-shaped germ, called a spirochete, Treponema pallidum. Spirochetes enter the body through breaks in the skin or through the mucous membranes, regardless of how they are transmitted. Once spirochetes enter the body, they spread rapidly. During the first four to six weeks after infection—that is, in its primary phase—syphilis is very contagious. During this time, it is identified by the appearance of a sore, or chancre, at the entry site of the infecting spirochetes. The chancre disappears quickly, and within six to twenty-four weeks, the disease shows itself as a skin rash, feelings of malaise, and other flulike symptoms (secondary syphilis). These problems also disappear quickly in most cases, and latent syphilis begins. In latent syphilis, the individual has no symptoms, but spirochetes are spreading through the body. If they localize in the brain or the heart, they produce paralysis, mental derangement, and/or death. A person in this stage of syphilis can still infect sexual partners.

Today, the cure for syphilis is simple, consisting of treatment with penicillin or other types of antibiotics. Very frequently, such treatment is carried out in a venereal disease clinic or in the office of a family physician.

Because one of the most serious results of syphilis is infection of unborn children, Americans who apply for marriage licenses are required to prove that they are free of the disease, and obstetricians routinely test their pregnant patients for the disease. The early detection of syphilis remains very important because no vaccine is yet available against the disease.

The first viable test for syphilis was originated by August von Wassermann in 1906. In this test, blood samples are taken and treated in a medical laboratory. The treatment of the samples is based on the fact that the blood of afflicted persons has formed antibodies to fight Treponema pallidum, and these antibodies can react with other substances (an extract of lipid—fatlike—body chemicals) that cause changes in the blood component called complement. When this reaction occurs, complement is said to be “fixed” and the test is positive. After syphilis is cured, the antibodies disappear and complement is no longer fixed, so the Wassermann test becomes negative.

The Wassermann test Wassermann test is a useful indicator of syphilis in 95 percent of all infected persons, but it is also very time-consuming (requiring a two-day incubation period), complex, and somewhat lacking in sensitivity. In 1923, serologist and immunologist Reuben Leon Kahn developed a modified syphilis test, the “standard Kahn test,” Kahn test that was simpler, faster, and more sensitive. This test, which is based on the reaction of serum from the tested individual with an extract of certain lipid components of beef heart, is complete after a few minutes. By 1925, Kahn’s test had become the standard syphilis test used by the U.S. Navy and later was employed worldwide for the detection of the disease.


Kahn soon realized that his test for syphilis was not perfect, however. For example, in some cases, related to other diseases, false positive reactions and false negative reactions occurred. This led him to a broader study of the immune reactions that produced the Kahn test. He investigated the role of various tissues in immunity, as differentiated from the role of blood antibodies and white blood cells. Kahn showed, for example, that different tissues of immunized and nonimmunized animals possessed differing immunologic capabilities. Furthermore, the immunologic capabilities of test animals varied with their ages, being very limited in newborns and increasing as they matured.

By 1951, this effort led to Kahn’s development of the “universal serological reaction,” Universal serological reaction a precipitation reaction in which blood serum is tested against reagent composed of tissue lipids. Kahn viewed the reaction as a “potential serologic indicator of various situations in health and in different diseases.” This effort constitutes an important landmark in the development of the science of immunology.

As W. Montague Cobb has noted, Kahn’s scientific contributions represent three investigative careers: The first was the development of his practical, rapid precipitation test for syphilis and special procedures that helped to clarify reactions with lipid antigens (1920 to 1928), the second was a study of tissue immunity that identified differences of tissue localization of bacteria and foreign proteins in test animals of different ages and immune states (1930 to 1957), and the third was a study of radiation effects on this tissue localization (1957 to 1973). Kahn is most widely known, however, for his efforts in the serological testing for syphilis. His endeavors also served to stimulate other developments in the field of immunology, including the VDRL test (originated by the Venereal Disease Research Laboratory), which replaced the Kahn test as one of the most often used screening tests for syphilis. Syphilis;testing
Medicine;syphilis treatment

Further Reading

  • Allen, Peter Lewis. The Wages of Sin: Sex and Disease, Past and Present. Chicago: University of Chicago Press, 2002. Discusses societal attitudes toward the victims of disease, especially sexually transmitted diseases, from the Middle Ages to the beginning of the twenty-first century. Chapter 3 looks specifically at responses to syphilis sufferers in early modern Europe. Includes bibliography and index.
  • Cobb, W. Montague. “Reuben Leon Kahn, D.Sc, LL.D., M.D., Ph.D.—1887.” Journal of the National Medical Association 63 (September, 1971): 388-394. One of the few available sources of biographical material on Kahn. Describes Kahn as both scientist and person, providing insight into his youth, education, and highlights of his life. Includes a complete list of Kahn’s publications.
  • Kahn, Reuben L. The Kahn Test: A Practical Guide. Baltimore: Williams & Wilkins, 1928. Presents a summary of the precipitation phenomenon in syphilis and a detailed discussion of the technical use of the Kahn test. Meant as a guide for laboratory workers, includes information on apparatus, reagents, standardization of the antigen, use of the test, procedure, and special aspects.
  • _______. “Rapid Precipitation Phase of the Kahn Test for Syphilis, with New Method for Indicating Results.” Journal of the American Medical Association 81 (July 14, 1923): 88-92. The original report of the Kahn test. Details the methodology and equipment utilized and indicates the advantages of the test over older methods and over Kahn’s own earlier efforts.
  • _______. Universal Serologic Reaction in Health and Disease. New York: Commonwealth Fund, 1951. Presents data to support Kahn’s contention that serologic reactions with lipid antigen are widely applicable as indicators of health and disease.
  • Parran, Thomas. Shadow on the Land: Syphilis. New York: Reynal & Hitchcock, 1937. Describes the impact of syphilis on U.S. public health and society in the early twentieth century. Includes a history of syphilis and discussion of its occurrence in North America and elsewhere.
  • Stansfield, William D. Serology and Immunology: A Clinical Approach. New York: Macmillan, 1981. Contains a comprehensive chapter on the etiology and serology of syphilis. Highly technical, rewarding information source for readers seeking details about methodology.
  • U.S. Public Health Service. Syphilis: A Synopsis. Washington, D.C.: Author, 2001. Brief text designed as a primer for physicians explains the tools of diagnosis and management of syphilis, the course of the disease, problems associated with congenital syphilis, and other topics.

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