Production and elimination of hyaluronan in rheumatoid arthritis patients: estimation with a loading test

To evaluate the benefit of determining the maximal elimination rate (Vmax) and the endogenous production of hyaluronan (HYA) in relation to the basal HYA concentration (c0) in rheumatoid arthritis (RA) patients; and to evaluate the compatibility of a new model for HYA kinetics, taking renal elimination into separate account in the overall clearance of HYA from the blood.

The calculations of production and elimination of HYA were based on the HYA loading test, which was performed in 21 patients with RA and 15 healthy controls. A blood sample was drawn before the loading test, followed by an intravenous (i.v.) injection of HYA as a single bolus dose of 7.5 mg. Blood samples were taken regularly during the next 60 minutes. A theoretical model with computational analysis of the data collected was used for calculating HYA production and elimination.

Patients with RA had significantly higher c0 than healthy controls, although in 10 of 21 patients c0 was within the normal range. The RA patients also had higher Vmax than healthy controls, but the difference was not significant. The calculated production of HYA was increased in RA patients (P = .001) and correlated with c0 (P < .0001). The new model for HYA kinetics, in which the renal elimination was taken separately into account, proved to be more compatible than the previous model.

The HYA loading test can help determine whether the increased serum level of HYA in RA patients is due to a high production or reduced elimination of HYA or both.