title: Elevated triglycerides may affect cystatin C recovery.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effect of triglyceride concentration on cystatin C (CysC) measurements.
  
  
  METHODS
  Serum samples collected from 10 nephrology patients, 43 to 78years of age, were air centrifuged to separate aqueous and lipid layers. The lipid layer from each patient was pooled together to create a mixture with a high triglyceride concentration. This pooled lipid layer was mixed with each of the ten patient aqueous layers in six different ratios. Single factor ANOVA was used to assess whether CysC recovery was affected by triglyceride levels. Regression analysis was used to develop a formula to correct for the effect of triglycerides on CysC measurement, based on samples from 6 randomly chosen patients from our study population. The formula was validated with the 4 remaining samples.
  
  
  RESULTS
  The analysis revealed a significant reduction in measured CysC with increasing concentrations of triglycerides (Pearson r=-0.56, p<0.0001). The following formula was developed to correct for the effect of triglycerides: Subsequent Bland-Altman plots revealed a bias (mean±1 standard deviation [SD]) of -3.7±15.6% for the data used to generate the correction formula and a bias of 3.52±9.38% for the validation set.
  
  
  CONCLUSIONS
  Our results suggest that triglyceride concentrations significantly impact cystatin C measurements and that this effect may be corrected in samples that cannot be sufficiently clarified by air centrifugation using the equation that we developed.
authors.affiliation: Department of Paediatrics, Children's Hospital, London Health Sciences Centre, University of Western Ontario, London, Ontario N6A 5W9, Canada.
authors.forename: Samantha H
authors.initials: SH
authors.lastname: Witzel
authors.affiliation: Department of Paediatrics, Children's Hospital, London Health Sciences Centre, University of Western Ontario, London, Ontario N6A 5W9, Canada; Department of Pathology and Laboratory Medicine, University of Western Ontario, London, Ontario, Canada.
authors.forename: Katherine
authors.initials: K
authors.lastname: Butts
authors.affiliation: Department of Paediatrics, Children's Hospital, London Health Sciences Centre, University of Western Ontario, London, Ontario N6A 5W9, Canada; Department of Pathology and Laboratory Medicine, University of Western Ontario, London, Ontario, Canada. Electronic address: guido.filler@lhsc.on.ca.
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
mesh_terms: D000328:Adult; D000368:Aged; D055316:Cystatin C / Q000097:blood* / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood* / Q000378:metabolism*
chemical_list: D055316:Cystatin C; D014280:Triglycerides
keywords: Cystatin C; Glomerular filtration rate; Hypertriglyceridemia; Nephrotic syndrome; Triglycerides