Serological Reactions in the Diagnosis of Rheumatoid Arthritis: (Evaluation of S.S.C., F II L.P. and B.F.T. Systems)

Summary The results of three agglutinating tests (S.S.C., F II L.P. and B.F.T.) concurrently performed in 151 patients with different diagnoses agreed in 81.5 % and disagreed in 18.5 %.In 54 patients with definite rheumatoid arthritis the S.S.C. was positive in 68.5%, the F II L.P. in 70.1 %, the B.F.T. in 61.1 %; the three tests agreed in 88.9 % and disagreed in 11.1 %; the highest correlation was noted between S.S.C. and F II L.P.In the group of definite rheumatoid arthritis, the greater was the number of diagnostic criteria present and the longer the duration, of the disease, the higher was the percentage of positive results obtained with all the three tests. There was a close correlation between the percentage of positive results and elevated ESR, presence of X-ray changes typical of rheumatoid arthritis and subcutaneous nodules.All the three tests gave a considerably higher percentage of positive results in the patients with probable and possible rheumatoid arthritis than in those with non-rheumatoid arthritis diseases. In this latter group S.S.C. was positive in 10.9 %, F II L.P. and B.F.T. in 1.8 %; S.S.C. gave the higher percentage of false-positive results and therefore must be considered less specific.The F II L.P. test seems to be the most sensitive and the easier in practical use.