Agglutination of sensitized sheep erythrocytes in disseminated lupus erythematosus.

In the course of our earlier investigations (Svartz, 1956a, b; Svartz and Schlossmann, 1953a, b, 1954, 1955, 1956) it was found that the cold precipitable protein fraction of serum from patients with active rheumatoid arthritis was able to agglutinate sheep erythrocytes sensitized with rabbit anti-sheep amboceptor. However, the haemagglutination titres of unfractionated sera, previously absorbed with normal sheep red cells-in the following pages denoted as whole serum-were sometimes found to be somewhat higher than those obtained with the cold precipitates, showing generally a single-tube difference in the end-point of agglutination. Comparative agglutination tests performed on cold precipitate from positive sera from patients with diseases other than rheumatoid arthritis showed haemagglutinating activity in the supernatant fluid but scarcely ever in the cold precipitable fraction. Thus, only a few cold precipitates other than those from rheumatoid arthritis showed haemagglutination, and then only those with a low titre. It should be added that in rheumatoid arthritis a varying amount of haemagglutinating factor could also be demonstrated in the supernatant fluid; the main point is that the rheumatoid factor (RF) can be precipitated in cold, whereas this happens only extremely rarely in the other collagen diseases. On the basis of earlier observations, it seemed obvious that the haemagglutination test performed with whole serum should be considered to be a laboratory procedure of great value for making differential diagnoses between rheumatoid arthritis and other joint diseases and collagen diseases. The introduction of the haemagglutination test with cold precipitate seemed to allow of a much safer differential diagnosis between rheumatoid arthritis and other conditions. In other words it made the haemagglutination test more "specific" to rheumatoid arthritis. Some recently published observations (Ziff, Brown, Lospalluto, Badin, and McEwen, 1956) suggest that patients with disseminated lupus 73 erythematosus quite frequently show clinical features of both disseminated lupus erythematosus and rheumatoid arthritis. Such patients showed positive L.E. cells as well as positive sheep red cell agglutination titres with both whole serum and cold precipitate. It should be kept in mind that the early stages of rheumatoid arthritis and atypical cases of disseminated lupus erythematosus not infrequently present diagnostic difficulties. Positive haemagglutination tests obtained with whole sera and re-dissolved cold precipitates from patients presumably suffering from disseminated lupus erythematosus with joint symptoms should be interpreted with caution. It is conceivable that such patients are suffering both from rheumatoid arthritis and lupus erythematosus, or from rheumatoid arthritis only, since L.E. cells can sometimes be demonstrated in true rheumatoid arthritis (Kievits, Goslings, and Schuit, 1956; Olhagen, 1957). The purpose of the present paper is to report on the results of our haemagglutination tests hitherto obtained with both whole serum and cold precipitable fraction from patients in whom the diagnosis of disseminated lupus erythematosus had been ascertained through the follow-up.