CLINICAL USEFULNESS OF SYNOVIAL-FLUID RHE UMATOID-FACTOR DETERMINATION - A REASSESSMENT

The aim of this work is to analyze the usefulness of rheumatoid factor determination in synovial fluid. One hundred twenty nine patients (29 with rheumatoid arthritis), in whom rheumatoid factor was simultaneou sly determined in serum and synovial fluid, were retrospectively analy zed. Serum rheumatoid factor had a 48% sensitivity, 98% specificity, 8 8% positive predictive value and 87% negative predictive value for the diagnosis of rheumatoid arthritis. These numbers were 76, 79, 51 and 92% respectively for synovial fluid rheumatoid factor- In rheumatoid a rthritis of less than one year of evolution, serum and synovial rheuma toid factor have a sensitivity of 15% and 62% respectively, a positive predictive value of 50 and 28% respectively and a negative predictive value of 90 and 94% respectively. It is thus concluded that the absen ce of rheumatoid factor in serum and synovial fluid in a patient with arthritis of less than one year of evolution, renders the diagnosis of rheumatoid arthritis very unlikely. Likewise the simultaneous presenc e of rheumatoid factor in both fluids has a high diagnostic certainty. Among other studied variables, leukocyte count, C3 and C4 levels in s ynovial fluid are the best discriminators within the different diagnos tic groups.