Clinical Correlates and Reference Intervals for Cystatin C in a Han Population from Southeast China.

BACKGROUND: Cystatin C (CysC) is an endogenous filtration marker for estimation of kidney function. This study aimed to define the reference interval (RI) for serum CysC in a southeast Chinese adult population and to explore the variables that affect serum CysC levels. METHODS: 532 reference individuals (259 male, 273 female, aged 18 - 79 years) were recruited from Guangzhou, China. Multiple regression analysis (MRA) was used to investigate the association between serum CysC levels and clinical factors including age, gender, body mass index, lifestyle, and biochemistry parameters. Reference values were defined using a parametric method according to Clinical and Laboratory Standards Institute guideline (C28A3). RESULTS: The mean serum CysC levels were significantly lower in females than in males (p < 0.001). Serum CysC levels increased with age (~0.047 mg/L increase per decade). MRA demonstrated that serum CysC levels correlated significantly with serum creatinine (Cr), high density lipoprotein (HDL-C), alkaline phosphatase (ALP), albumin (ALB), and uric acid (UA) concentrations, although their relationships were less prominent than those of gender or age. The RIs for serum CysC levels were calculated at 0.73 - 1.17 mg/L for subjects aged 18 - 49 years and at 0.73 - 1.49 mg/L for those aged 50 - 79 years. CONCLUSIONS: The RIs for serum CysC were established in a southeast Chinese population. In addition to gender and age, serum Cr, HDL-C, ALP, ALB, and UA also influenced serum CysC levels.

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

OBJECTIVES: Serum 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 METHODS: The 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. RESULTS: At CysC concentrations of 0.45 and 1.80mg/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 8.00mg/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 5g/L, bilirubin (free or conjugated) 200mg/L, or chyle 1500 formazin turbidity units. CONCLUSIONS: The 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.