Measurement of Soluble Pyrophosphate in Plasma and Synovial Fluid of Patients with Various Rheumatic Diseases

Abstract

Soluble pyrophosphate was measured in the plasma and synovial fluid of various groups of patients and in the plasma of two control groups. The two control groups consisted of 13 healthy subjects and 19 patients suffering from benign lumbar back pain. The other group of patients had rheumatoid arthritis (RA) (14 plasma and 19 synovial fluid examinations), osteoarthrosis (OA) (19 plasma and 26 synovial fluids) and articular chondrocaicinosis (ACC) (27 plasma and 43 synovial fluids). The level of soluble pyrophosphate in the plasma was 3.5 μmol/1 in healthy subjects, 4.0 μmol/1 in patients with lumbar back pain, 4.1 μmol/1 in individuals having OA and 3.5 μmol/1 in the group suffering from RA as well as for those with ACC. The differences between these values are not significant statistically. In the synovial fluid the values were 4.6 jimol/1 for the group with RA, 12.7 μmol/1 for those with OA and 34.2 μmol/l in the group having ACC. If a normal distribution of these values is assumed and the average values and standard deviations recalculated for each group after elimination of cases more than 3 standard deviations above the mean, then we obtain 9.8 μmol/1 for the group with OA and 23.8 p.mal/1 for those with ACC. The difference between the group with RA and that with OA is highly significant (p XJ. 001). Even more significant is the difference between the group with RA and ACC (p<0.0005). The difference between the OA and the ACC is also highly significant (p<0.001). On the basis of these observations various mechanisms leading to the pyrophosphage crystal deposition disease are discussed.