Serum cystatin C-immunoglobulin high-molecular-weight complexes in kidney and liver transplant patients

Background. It has been suggested recently that the glomerular filtration r ate (GFR) in renal transplant patients is underestimated by serum cystatin C clue to all impaired filtration of complexed cystatin C with immunoglobul ins. Consequently, serum cystatin C may not be a reliable marker of GFR in these patients. Our study was designed to determine whether this suppositio n is correct. Methods. In 87 serum samples from patients with various kidney diseases. 18 2 samples from renal transplant patients, and 72 samples from liver transpl ant patients, the concentrations of cystatin C and creatinine were determin ed, as well as the residual concentration of cystatin C after precipitation of macromolecules with polyethylene glycol (PEG; 6000 molecular weight). Results. The residual concentration of serum cystatin C after precipitation with PEG in all cases was much higher (70 to 100%) than that expected in t he case of the existence of cystatin C-immunoglobulin complexes. In the kid ney and liver transplant patients, there was no significant correlation bet ween the residual concentration of cystatin C and the postoperative time (r = -0.098). Conclusions. The results suggest that in renal or liver transplant patients there is no formation of high molecular weight serum cystatin C-immunoglob ulin complexes, regardless of the post-transplant period.