To evaluate the prognostic value of some synovial fluid variables in patients with rheumatoid arthritis.
Twenty-nine patients with erosive rheumatoid arthritis and hydropsy in a knee joint were followed for 7.5 years in a prospective study. At the start of the study the knee joints were aspirated and 15 synovial fluid variables were analyzed. The patients were divided into two groups according to whether or not there had been progress of radiologically detected destruction in the knee joints during the follow-up.
Of the synovial fluid variables at the start, only C3 (p = 0.030) and acid phosphatase (p = 0.047) differed significantly between the groups, the former being lower and the latter higher in patients with deterioration of knee joints.
These preliminary results may indicate that low synovial fluid C3 and high acid phosphatase predict poor prognosis in a joint affected by rheumatoid arthritis.