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 and materials. 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 ≤ 2.0%, between-run CVs ≤ 4.2%, and total CVs ≤ 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 μmol/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. Conclusion. The performance of the Tina-quant Cystatin C assay was acceptable for clinical use.

Key Words::

• Cysteine proteinase inhibitors
• glomerular filtration rate
• immunoassay
• kidney function tests
• turbidimetry

Acknowledgements

The authors are grateful to Mrs Lena T. Pedersen for excellent technical assistance.

This study was supported by a grant from the Foundation of Rosa and Asta Jensen.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.