Performance characteristics of a cystatin C immunoassay with avian antibodies

A new particle-enhanced turbidimetric immunoassay (PETIA) with avian antibodies for measuring serum/plasma cystatin C has been developed. The performance characteristics of the assay are described.

Measurements were performed on a Roche Modular P and on an Abbott Architect ci8200 using Gentian cystatin C immunoassay.

Measuring range was 0.3-8.0 mg/L. Reference range was 0.57-1.09 mg/L. Total analysis time was 10 minutes. Linearity was absolute over the whole assay range. Recovery of samples and controls was within 98.6-109.4%. Total imprecision CV, measured over 20 days with two lots, was < or = 4.2%. Comparison with a particle enhanced nephelometric cystatin C immunoassay (PENIA) by linear regression resulted in a slope within 0.97-1.02 and intercept within +/-0.05 mg/L. Interference studies with drugs, anticoagulants, intralipid (< or = 11 g/L), triglycerides (< or = 14 g/L) and bilirubin (< or = 420 mg/L) showed no significant interference. Due to the use of avian antibodies, no interference with rheumatoid factor was observed. No carry-over was detected. Lower detection limit and lower quantification limit (CV < or = 6%) were both below 0.33 mg/L, which is less than the lowest standard. Sample stability was up to one month at 2-8 degrees C. Stability of the reagents at 2-8 degrees C was estimated to be 24 months. Stability of the reagents in use was minimum 9 weeks.

Gentian cystatin C PETIA is shown to have excellent performance between methods . Interference results are improved due to avian antibodies and a broader span of the calibration curve. Avian antibodies are also known to have better immune response than mammalian antibodies towards mammalian antigens.