Performance evaluation of a turbidimetric cystatin C assay on different high-throughput platforms.
OBJECTIVE
The goal with this study was to evaluate the analytical performance of a new cystatin C immunoassay (Tina-quant a Cystatin C, Roche Diagnostics GmbH). The evaluation was carried out at four centers according to a standardized protocol.


METHODS
The Tina-quant a Cystatin C is a latex particle-enhanced immunoturbidimetric assay. Roche cobas 6000, MODULAR ANALYTICS SWA and COBAS INTEGRA instruments were included in the study. Method comparison studies were carried out against two turbidimetric methods (Dako Cystatin C, Gentian Cystatin C), and one nephelometric method (Siemens N-Latex Cystatin C).


RESULTS
Linearity was proven throughout the measuring range from 0.4 to 8 mg/L. Within-run CVs ranged from 0.7-2.8%, and total CVs from 1.4-4.7 % (concentration range 0.6-3.9 mg/L). Comparable results were obtained with paired serum and Li-heparinate plasma samples. Good agreement was achieved in the comparisons between the Tina-quant a Cystatin C assay and the other commercially available cystatin C assays, two different turbidimetric methods (slope range 0.88-1.04, intercept < 0.17 mg/L, r > or = 0.993) and one nephelometric assay (slope range 0.90-1.05, intercept < 0.21 mg/L, r > or = 0.986).


CONCLUSIONS
The Tina-quant a Cystatin C assay was shown to be precise and accurate with proven linearity over the measuring range. Good comparability was obtained with other commercially available assays for the determination of cystatin C. The Tina-quant a Cystatin C assay is very well suited for clinical use on routine clinical chemistry analysers to detect renal dysfunction with a 24 h availability.
Hansson
Lars-Olof
LO
Department of Laboratory Medicine, Karolinska University Hospital, Stockholm, Sweden.
Grubb
Anders
A
Lidén
Anders
A
Flodin
Mats
M
Berggren
Annacarin
A
Delanghe
Joris
J
Stove
Veronique
V
Luthe
Hilmar
H
Rhode
Karl-Heinz
KH
Beck
Claus
C
Domke
Ingrid
I
D001322:Autoanalysis; D055316:Cystatin C / Q000097:blood*; D005919:Glomerular Filtration Rate; D007118:Immunoassay / Q000379:methods; D007674:Kidney Diseases / Q000175:diagnosis; D007677:Kidney Function Tests / Q000379:methods; D009391:Nephelometry and Turbidimetry; D015203:Reproducibility of Results
D055316:Cystatin C