title: Particle enhanced turbidimetric immunoassay for the determination of urine cystatin C on Cobas c501.
abstract: OBJECTIVE
  Urinary cystatin C has been reported to be a good marker for tubular damage and acute kidney injury. The aim of this study was to develop a high throughput assay for the quantification of urine cystatin C.
  
  
  METHODS
  Antigen-excess, imprecision, interference, linearity, recovery, sample stability and reference values were evaluated on Cobas c501.
  
  
  RESULTS
  The assay was linear over the dynamic range of the study (R²=0.9994). The total assay imprecision was below 5%. The assay recovery was estimated at 87-100%. No tendency to antigen-excess (up to 35 mg/L), nor interference with haemoglobin (1.25-10 g/L) was observed. Cystatin C was stable for 1 day at ambient temperature (19-23°C) but for 2 days at +4°C. The reference interval for cystatin C in urine was <0.414 mg/L.
  
  
  CONCLUSIONS
  The urinary cystatin C assay verified to be a reliable assay with convenient performance characteristics, enabling routine testing on clinical chemistry platforms.
authors.affiliation: Section of Clinical Chemistry, Department of Medical Sciences, Uppsala University, Uppsala, Sweden. Azita.Sohrabian@akademiska.se
authors.forename: Azita
authors.initials: A
authors.lastname: Sohrabian
authors.forename: Feria Hikmet
authors.initials: FH
authors.lastname: Noraddin
authors.forename: Mats
authors.initials: M
authors.lastname: Flodin
authors.forename: Annika
authors.initials: A
authors.lastname: Fredricsson
authors.forename: Anders
authors.initials: A
authors.lastname: Larsson
mesh_terms: D000328:Adult; D057205:Automation, Laboratory / Q000295:instrumentation; D002138:Calibration; D055316:Cystatin C / Q000652:urine*; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
chemical_list: D055316:Cystatin C