Analytical Performance of a Particle-enhanced Nephelometric Immunoassay for Serum Cystatin C Using Rate Analysis
| Autor: | David J. Newman, Helen J. Stowe, Edmund J. Lamb, David Lawrence |
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| Rok vydání: | 2001 |
| Předmět: | |
| Zdroj: | Clinical Chemistry. 47:1482-1485 |
| ISSN: | 1530-8561 0009-9147 |
| DOI: | 10.1093/clinchem/47.8.1482 |
| Popis: | The serum cystatin C concentration reflects glomerular filtration and, as a marker of renal disease, demonstrates improved accuracy and sensitivity compared with serum creatinine (1)(2)(3). Several assays (4) have been described for cystatin C, including latex particle-enhanced nephelometric immunoassays (PENIAs) (5) and turbidimetric immunoassays (PETIAs) (2)(3). The PETIA marketed by Dako Ltd (cat. no. K 0071; Ely, United Kingdom) has been adapted to a variety of automated analyzers that use fixed-interval turbidimetric measurement (6)(7). However, the analytical performance initially described for this method (2) has not always been replicated. Compared with the PENIA developed for the Dade Behring (Milton Keynes, United Kingdom) nephelometers [e.g., the Behring Nephelometer II (BNII)], the PETIA demonstrates high imprecision at the upper limit of the reference interval (6)(8)(9) and susceptibility to spectral interferences (4). On a Cobas Mira S Plus analyzer, these reagents were subject to interference from bilirubin (>270 μmol/L), hemoglobin (>4 g/L), and triglycerides (>5.7 mmol/L), and between-day imprecision (CV) exceeded 8% at 1.10 and 4.10 mg/L (10). We describe the measurement of cystatin C using an adaptation of these reagents in a nephelometric immunoassay using kinetic rate analysis. All analyses were performed with a single batch of reagent on an automated rate nephelometer (ImmageTM analyzer; Beckman-Coulter Ltd., High Wycombe, United Kingdom). Recombinant human cystatin C calibrators supplied by the manufacturer were used, and an additional calibrator was prepared by diluting (1:1) the calibrator with the lowest cystatin C concentration (0.39 mg/L) in phosphate buffer, pH 7.0 (cat. no. 447640; Beckman-Coulter Ltd.). The calibrator with the highest concentration (12.3 mg/L) was not used. Analyses were performed in user-defined mode, using provisional settings provided by the instrument manufacturer. Briefly, sample was diluted 1:5 with phosphate buffer. Reagent buffer (195 μL) … |
| Databáze: | OpenAIRE |
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