Performance evaluation of a particle-enhanced turbidimetric cystatin C assay on the Hitachi 917 analyzer.
BACKGROUND
Human cystatin C is a low molecular weight protein that has been proposed as a new endogenous marker of glomerular filtration rate. We investigated the performance of the Genzyme cystatin C assay on the Hitachi 917 analyzer.


METHODS
Imprecision, linearity, recovery, and interference studies were performed on the Hitachi 917 analyzer. For method comparison, split sample aliquots were assayed using the described method and 2 other commercially available cystatin C assays.


RESULTS
The assay was linear from 0.24 to 6.36 mg/l. Within-run coefficient of variation (CV) was 4.2 and 0.8% at cystatin C concentrations of 0.50 and 2.00 mg/l, respectively. Between-run CV was 4.3 and 2.7% at the same concentrations. The average analytical recovery was 99%. Bilirubin (< or =30 mg/dl), triglycerides (< or =1000 mg/dl), intralipid (L index < or =1000), and rheumatoid factor (< or =1000 IU/ml) did not interfere with the assay. A >10% change in cystatin C level was observed when hemoglobin concentration was >800 mg/dl. The assay compared well with the Dade Behring immunonephelometric assay and the Dako immunoturbidimetric assay.


CONCLUSIONS
The Genzyme cystatin C immunoassay is an acceptable method for the determination of cystatin C on the Hitachi 917 analyzer.
Al-Turkmani
M Rabie
MR
Department of Laboratory Medicine, Children's Hospital Boston and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States.
Law
Terence
T
Kellogg
Mark D
MD
D001663:Bilirubin / Q000097:blood; D002138:Calibration; D055316:Cystatin C / Q000032:analysis*; D005217:Fat Emulsions, Intravenous / Q000032:analysis; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007120:Immunochemistry; D007155:Immunologic Factors / Q000097:blood; D007202:Indicators and Reagents; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D015203:Reproducibility of Results; D012217:Rheumatoid Factor / Q000097:blood; D014280:Triglycerides / Q000097:blood
D055316:Cystatin C; D005217:Fat Emulsions, Intravenous; D006454:Hemoglobins; D007155:Immunologic Factors; D007202:Indicators and Reagents; D014280:Triglycerides; D012217:Rheumatoid Factor; D001663:Bilirubin