title: Performance evaluation of the Roche Tina-quant Cystatin C assay and reference interval for cystatin C in healthy blood donors.
abstract: OBJECTIVE
  To evaluate the performance of the Roche Diagnostics Tina-quant Cystatin C particle enhanced immuno turbidimetric assay for the measurement of plasma and serum cystatin C, and to establish reference intervals for cystatin C in healthy blood donors.
  
  
  METHODS
  The cystatin C measurements were performed on the Roche Modular Analytics P automated clinical chemistry analyzer.
  
  
  RESULTS
  The cystatin C assay was linear in the measuring range 0.40-7.00 mg/L. Within-run CVs < or = 2.0%, between-run CVs < or = 4.2%, and total CVs < or = 5.5% in plasma pools and in commercial cystatin C control materials (range 1.0-4.7 mg/L). Recovery was 99.4-109.3%. No interference was detected from haemoglobin < 0.9 mmol/L, bilirubin < 330 micromol/L and Intralipid < 20 g/L. Measurement of cystatin C in Li-heparin plasma did not differ significantly from cystatin C measured in serum. Forty patient samples run on the Modular Analytics P (y) were compared to the Siemens Cystatin C assay on the BN II (x): y = 0.817x + 0.270, Sy.x = 0.168 (Deming regression). The non-parametric reference interval for cystatin C was calculated to be 0.41-0.91 mg/L in females (n = 86), and 0.43-0.94 mg/L in males (n = 76). The Mann-Whitney U test showed a significant difference between the two genders (p = 0.015), but the difference was without clinical relevance. A common reference interval for both genders (n = 162) was calculated to be 0.41-0.92 mg/L.
  
  
  CONCLUSIONS
  The performance of the Tina-quant Cystatin C assay was acceptable for clinical use.
authors.affiliation: Department of Clinical Biochemistry, Viborg Regional Hospital, Viborg, Denmark. erland.erlandsen@viborg.rm.dk
authors.forename: Erland J
authors.initials: EJ
authors.lastname: Erlandsen
authors.forename: Else
authors.initials: E
authors.lastname: Randers
mesh_terms: D000328:Adult; D000368:Aged; D001782:Blood Donors; D055316:Cystatin C / Q000097:blood / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D012016:Reference Values; D012737:Sex Factors; D055815:Young Adult
chemical_list: D055316:Cystatin C