title: Intra-individual variation of cystatin C and creatinine in pediatric solid organ transplant recipients.
abstract: There is controversy about the feasibility of cystatin C (CysC) as a marker of glomerular filtration rate (GFR) post-transplant (Tx). We studied intra-patient variability of CysC in comparison with serum creatinine (SCr) in 20 children (11 males, mean age 11.5 +/- 6.4 yr) with solid organ transplants (14 kidney, four liver, and two combined liver + kidney transplants). The mean age at Tx was 7.0 +/- 5.6 yr. A total of 178 simultaneous SCr and CysC measurements (median 8 per patient) were analyzed. In addition, GFR was calculated using the Schwartz and a novel CysC-based formula. Intra-individual coefficient of variations (CV) was calculated as ratio of standard deviation over mean. The mean CV was significantly lower for SCr (7.71 +/- 4.16%) when compared with CysC (10.27 +/- 4.87, p = 0.04), but was no longer significantly different when excluding patients with a bladder augment. The CV of the GFR estimated by Schwartz formula (7.44 +/- 3.77) was significantly lower than GFR calculated from CysC (12.52 +/- 7.37), p = 0.001. The mean ratio between the Schwartz GFR and the GFR calculated from CysC was 102.6 +/- 12.8%, not significantly different from 100% (p = 0.3796). The only potential confounding factors to explain increased CV after Tx were gender and bladder augmentation, whereas calcineurin inhibitors or steroids did not influence CV. With the limitation of a small number of subjects, our data suggest that the CysC and the CysC-calculated GFR is equivalent but not better than SCr and Schwartz formula. We therefore conclude that measurement of CysC can be used for longitudinal intra-individual follow-up of renal function post-Tx.
authors.affiliation: Department of Pediatrics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Ludmila
authors.initials: L
authors.lastname: Podracka
authors.forename: Janusz
authors.initials: J
authors.lastname: Feber
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lepage
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
mesh_terms: D002648:Child; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007677:Kidney Function Tests; D016030:Kidney Transplantation; D016031:Liver Transplantation; D008297:Male; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D007166:Immunosuppressive Agents; D003404:Creatinine