title: Validation of a new standardized cystatin C turbidimetric assay: evaluation of the three novel CKD-EPI equations in hypertensive patients.
abstract: OBJECTIVE
  Analytical and clinical performances of the new standardized cystatin C particle-enhanced turbidimetric immunoassay (PETIA) using DiaSys reagents on Olympus AU2700® analyzer were evaluated.
  
  
  METHODS
  We have studied imprecision, linearity, limit of detection and limit of quantification of this new immunoassay. Method comparison was assessed in relation to results generated by the standardized Siemens-particle-enhanced nephelometric immunoassay (PENIA). In order to evaluate the clinical relevance of this assay, estimated glomerular filtration rate (GFR) was calculated using MDRD, CKD-EPI creatinine, CKD-EPI cystatin C 2012 and CKD-EPI creatinine-cystatin C 2012 equations and compared to GFR measured using urinary clearance of (99m)Tc-DTPA in 100 hypertensive patients.
  
  
  RESULTS
  Cystatin C measurements using DiaSys reagents have reliable analytical performances and are comparable to the standardized Siemens-PENIA method (bias of 0.01 mg/L). The mean measured GFR was 90.0±29.7 mL/min/1.73 m². Bias and accuracy of the three CKD-EPI equations were better than the MDRD. Both CKD-EPI creatinine-based and cystatin C-based formulae had similar bias, precision and accuracy. The combined creatinine-cystatin C equation was significantly more accurate and precise than the CKD-EPI creatinine equation in patients with GFR above 60 mL/min/1.73 m².
  
  
  CONCLUSIONS
  The use of cystatin C in a combined equation with creatinine could improve the accuracy of eGFR in the reference interval.
authors.affiliation: Laboratoire de Biochimie, CHRU Montpellier, Univ Montpellier 1, Montpellier F-34000, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Obiols
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Bargnoux
authors.forename: Nils
authors.initials: N
authors.lastname: Kuster
authors.forename: Pierre
authors.initials: P
authors.lastname: Fesler
authors.forename: Laurence
authors.initials: L
authors.lastname: Piéroni
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Badiou
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Dupuy
authors.forename: Jean
authors.initials: J
authors.lastname: Ribstein
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Cristol
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000175:diagnosis; D007118:Immunoassay / Q000592:standards*; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009391:Nephelometry and Turbidimetry; D016284:Technetium Tc 99m Pentetate / Q000031:analogs & derivatives / Q000652:urine
chemical_list: D015415:Biomarkers; D055316:Cystatin C; C481867:technetium Tc 99m diethylene triamine pentaacetic acid, dimethyl ester; D003404:Creatinine; D016284:Technetium Tc 99m Pentetate
keywords: CKD-EPI equations; Glomerular filtration rate; Standardized cystatin C