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

Abstract

Background. It has been suggested recently that the glomerular filtration rate (GFR) in renal transplant patients is underestimated by serum cystatin C due to an impaired filtration of complexed cystatin C with immunoglobulins. Consequently, serum cystatin C may not be a reliable marker of GFR in these patients. Our study was designed to determine whether this supposition is correct. Methods. In 87 serum samples from patients with various kidney diseases, 182 samples from renal transplant patients, and 72 samples from liver transplant patients, the concentrations of cystatin C and creatinine were determined, 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 the case of the existence of cystatin C-immunoglobulin complexes. In the kidney and liver transplant patients, there was no significant correlation between 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-immunoglobulin complexes, regardless of the post-transplant period.