While the serologic properties of blood of patients with rheumatoid arthritis have been studied extensively, no test of diagnostic value has, as yet, been devised. 7 Such a laboratory test would have considerable significance were it to confirm or eliminate an early rheumatoid state. In 1939 Waaler demonstrated in the serum of some persons a factor which agglutinated sheep red blood cells. A small amount of such serum, when added to specific agglutinating serum against sheep red cells, increased the titer of the specific serum remarkably. If a small amount of anti-sheep cell serum is added to one of these human serums, agglutination of sheep red blood cells will occur in high dilutions, whereas no agglutination appears without the addition of the specific agglutinating serum. This factor was found, in small amounts, in serums of patients with various diseases. I t was found in larger quantities in 22 of 43 patients (51 per cent) with rheumatoid arthritis. It was further demonstrated that this hitherto unknown factor was present in the globulin fraction of the serum, was relatively thermostable (withstanding 60 C. for one-half hour), and was not related to the heterophile antibodies or to the patient's blood group. These interesting observations, to our knowledge, did not provoke any further clinical or bacteriologic investigation. In 1948, however, Rose and his associates described a similar phenomenon in the serum of patients with rheumatoid arthritis. When inactivated human serums were set up in serial dilutions and tested against normal sheep erythrocytes and sensitized sheep erythrocytes, they disclosed that a sixteen-f old or greater increase in the agglutination of the sensitized cells occurred almost exclusively in patients with rheumatoid arthritis; in other forms of arthritis the reactions were much milder. These observers considered that the height of the differential titer reflected the clinical activity of the disease. Moreover, utilizing electrophoretic technics, this specific factor was demonstrated in the beta and gamma globulin fractions of the serum, and appeared to be unrelated to the antibody responsible for the Group A hemolytic streptococcus agglutination test. In a series of 51 patients exhibiting some form of rheuma toid arthritis, a positive serologic test was found in 38 patients (74.5 per cent). In 15 patients with rheumatic fever and in 15 other patients with arthritic manifestations, which included undifferentiated arthritis of mild character, degenerative joint disease, dermatomyositis, lupus erythematosus disseminatus, gout, gonorrheal arthritis, lymphopathia venereum and Sudeck's atrophy, the test was negative. An additional 29 patients, with a variety of diseases, free of arthritic manifestations or involvement, were also examined and in only 2 instances (7 per cent) was a positive reaction observed.
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