Cystatin C

The Cystatin C assay is an in vitro diagnostic test that measures cystatin C levels in human serum and plasma using a particle-enhanced turbidimetric immunoassay (PETIA) on the Alinity c system. It is used to aid in the diagnosis and treatment of renal diseases and is intended for laboratory professional use only.

Both devices use immunoturbidimetric methodology and PETIA principles on the same specimen types (serum and plasma). Key differences include: subject device has a wider analytical measuring interval (0.30–10.00 mg/L vs 0.40–6.80 mg/L), extended measuring interval to 40 mg/L vs 10.20 mg/L, lower limits of measurement (LoB 0.03 vs 0.30 mg/L), and runs on Alinity c system versus Roche/Hitachi cobas c 501. Both are standardized to ERM-DA471/IFCC.

CLSI EP05-A3 (precision), CLSI EP06 (linearity), CLSI EP07 (interference testing), CLSI EP09c (method comparison), CLSI EP17-A2 (limits of detection), and CLSI EP28-A3c (reference intervals). Accuracy was assessed against certified reference material ERM-DA471/IFCC.

The subject device and predicate device share identical intended use, specimen types, methodology, and assay principle. Nonclinical performance testing demonstrates acceptable precision (within-laboratory %CV 0.6–1.8%), accuracy (bias 1.3–1.8%), linearity across the analytical measuring interval, and minimal interference from endogenous and exogenous substances. Method comparison shows excellent correlation (r=1.00) with a comparator assay. The extended measuring interval and improved lower limits of measurement represent enhanced capabilities that do not raise new safety or effectiveness concerns and remain clinically relevant for renal disease assessment.