Abderhalden is known for a
blood test for pregnancy, a test for
cystine in urine, and for explaining the
Abderhalden–Kaufmann–Lignac syndrome, a recessive genetic condition. He did extensive work in the analysis of proteins, polypeptides, and enzymes. His
Abwehrfermente ("defensive enzymes") theory stated that immunological challenge will induce the production of
proteases. This was seemingly "proven" by many collaborators in Europe, although attempts to verify the theory abroad failed. The pregnancy test was determined to be unreliable a few years after its inception. In late 1912 Abderhalden's "defensive ferments reaction test" was applied to the differential diagnosis of
dementia praecox from other mental diseases and from normals by Stuttgart psychiatrist August Fauser (1856–1938), and his miraculous claims of success were soon replicated by researchers in Germany and particularly in the United States. However, despite the worldwide publicity this "blood test for madness" generated, within a few years the "Abderhalden–Fauser reaction" was discredited and only a handful of American psychiatric researchers continued to believe in it. Certainly by 1920 the test was all but forgotten in the USA. Abderhalden's reputation continued to grow in Germany, however, where collaborators managed to "replicate" his results, usually by simply repeating experiments until they succeeded and discarding the negative results. As Abderhalden was seen as the founder of scientific biochemistry in Germany, questioning his work could harm one's career, as
Leonor Michaelis, who had been a collaborator with Abderhalden, discovered when he reported inability to reproduce Abderhalden's claims for his pregnancy test; by 1922, Michaelis's situation in Germany was so tarnished that he had to leave the country to embark on an outstanding career of scientific success abroad. Otto Westphal described Abderhalden's work in conversation with
Ute Deichmann as follows: the entire extent of the rejection was revealed. However, in Abderhalden's days, the science of
immunology was all but non-existent. That his experiments indeed seemed to "work" on occasion was probably due to
immunoprecipitation. The crucial difference between this and Abderhalden's theory is that the former is an effect of
antibodies, whereas the fictitious
Abwehrfermente were presumed to be
proteases; a difference that has large implications for biochemistry and immunology. The most comprehensive analysis of the issue as to whether Abderhalden was simply grossly mistaken or perpetuated deliberate fraud can be found in Kaasch. == Personal life ==