Performance evaluation of the Sysmex Cystatin C assay on the Roche Modular P Analyzer

• Evaluation of the performances of an automated assay for Cystatin C testing.
• The Sysmex Cystatin C assay showed good precision, linearity, and recovery.
• The Sysmex assay were free from hemoglobin, bilirubin, or chyle interferences.
• The Sysmex assay demonstrated good agreement with Roche and Siemens assays.

ObjectivesSerum Cystatin C (CysC) is a promising endogenous marker for estimation of glomerular filtration rate. This study evaluated the analytical performance of the Sysmex CysC assay on the Roche Modular P Chemistry Analyzer (Modular P).Design and methodsThe evaluation of imprecision, linearity, recovery, and interference were performed in accordance with the relevant Clinical and Laboratory Standards Institute guidelines protocols, using quality controls and patient samples. Comparison studies were conducted against the Siemens and Roche assay for CysC.ResultsAt CysC concentrations of 0.45 and 1.80 mg/L, the within-run coefficient of variations (CVs) were 2.81% and 2.04%, respectively, and the between-run CVs were 3.14% and 3.26%. The CysC assay was proven throughout the measuring range from 0.10 to 8.00 mg/L. Good correlations were achieved among the 3 CysC assays. The Sysmex assay appeared to report higher results than the Siemens assay. No interference was detected from hemoglobin 5 g/L, bilirubin (free or conjugated) 200 mg/L, or chyle 1500 formazin turbidity units.ConclusionsThe Sysmex CysC assay performed well with regard to basic performance, including precision, dilution linearity, and effects of interfering substances, and is an acceptable assay for the determination of CysC on the Modular P.