The Dade Behring N Latex Cystatin C assay, a particle-enhanced nephelometric immunoassay for measuring serum cystatin C, was evaluated on the Dade Behring Nephelometer II. The assay time was 6 min and the throughput was 75 samples per hour. The sample volume was 40 microL and the measuring range was 0.25-7.90 mg/L. Imprecision studies revealed within-run CVs < 1.8% and between-run CVs < 1.8% in the concentration range 0.87-4.63 mg/L. Recovery was 92.4-101.3%. Linearity studies showed excellent correlation between the theoretical and obtained values. No interferences were detected from haemoglobin < 1.0 mmol/ L, bilirubin <512 micromol/L and Intralipid <20 g/L. Stability of cystatin C in serum was 7 days at temperatures from 20 degrees C to 20 degrees C and 6 months at -80 degrees C. Measurements of cystatin C in heparin-plasma and EDTA-plasma did not differ significantly from cystatin C measured in serum. Fifty patient samples run on the Dade Behring Nephelometer II (y) were compared to the Dako Cystatin C assay (x). The Passing-Bablok regression analysis revealed y = 1.105x - 0.340. In conclusion, the Dade Behring N Latex Cystatin C assay was precise and correlated with the Dako Cystatin C assay.

Objective: To investigate the relationship between serum cystatin C, serum creatinine, and 51 Cr-EDTA-clearance in patients with spinal cord injury. Setting: The Spinal Cord Unit, Viborg-Kjellerup County Hospital. Methods: Twenty-four men and seven women aged 20.3 to 68.0 years with motor complete spinal cord injury (ASIA A or B) were included. Serum cystatin C was measured by an automated particle-enhanced nephelometric immunoassay (Dade Behring), serum creatinine by an enzymatic method (Vitros 950), and 51 Cr-EDTA-clearance by a multiple plasma sample method. Results: A linear relationship was found between 51 Cr-EDTA-clearance and the reciprocal values of cystatin C and creatinine. The correlation coe cient between 51 Cr-EDTA-clearance and 1/cystatin C was 0.72 compared to the correlation coe cient between 51 Cr-EDTAclearance and 1/creatinine being 0.26. Comparison of the area under the curves in the nonparametric receiver operating characteristics (ROC) plots for serum cystatin C (area under the curve (AUC)=0.912; SE=0.065), and serum creatinine (AUC=0.507; SE=0.115) revealed signi®cant di erences (P-values=0.0005). Conclusion: In patients with spinal cord injury serum cystatin C is a better marker of the renal function compared to serum creatinine.