Macromolecular Complexes of Cystatin C With Circulating Liver Plasma Membrane Fragments and Determination of Serum Cystatin C Using the Particle Enhanced Nephelometric Immunoassay (PENIA) in Kidney and Liver Transplantation and Biliary Obstructio n
Bouzas, L.; J Carlos Tutor
Clinical Laboratory 57(3-4): 207-212
2011
ISSN/ISBN: 1433-6510 PMID: 21500728 Document Number: 13427
Background: In a patient with biliary obstruction, a macromolecular complex of cystatin C with liver plasma membrane fragments, which also contain several membrane-bound enzymes, which may be removed by butanol extraction, has recently been characterised. This could lead to an underestimation of the glomerular filtration rate (GFR) from serum cystatin C concentration. Methods: Using the particle enhanced nephelometric immunoassay (PENIA), serum cystatin C concentration was determined in 50 healthy controls, 43 patients with renal insufficiency, 68 kidney and 88 liver transplant recipients, and 60 patients with biliary obstruction. Residual cystatin C concentrations and Γ-glutamyltransferase (GGT) activities after butanol extraction were also determined. Results: In the controls and patients with renal insufficiency the residual concentrations of cystatin C after butanol extraction were always ≥ 80 %. However, in 2 renal and 7 liver transplant recipients and in 11 patients with biliary obstruction this biochemical variable was Conclusions: These results suggest that in the cases with residual cystatin C concentrations < 80 % after butanol extraction, presumably due to the presence of circulating macromolecular cystatin C, the serum levels of cystatin C obtained using the PENIA assay do not lead to a systematic GFR underestimation.
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