title: 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.
authors.affiliation: Laboratorio Central y Servicio de Nefrología, Hospital Clínico Universitario de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Hermida
authors.forename: R
authors.initials: R
authors.lastname: Romero
authors.forename: J C
authors.initials: JC
authors.lastname: Tutor
mesh_terms: D000328:Adult; D000368:Aged; D011232:Chemical Precipitation; D055316:Cystatin C; D015891:Cystatins / Q000097:blood* / Q000737:chemistry; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000097:blood* / Q000737:chemistry; D016030:Kidney Transplantation; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D011092:Polyethylene Glycols; D011184:Postoperative Period; D012997:Solvents; D013997:Time Factors
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D007136:Immunoglobulins; D012997:Solvents; D011092:Polyethylene Glycols