Evaluation of an Automated Method for Cytokine Measurement Using the Immulite® Immunoassay System
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Franck Berthier
Abstract
Cytokines are key mediators in cell regulation and communication. The concentration of these proteins can rapidly and importantly increase during severe clinical situations. However, current techniques are not adapted to stat measurement, thus making their clinical use limited.
In this context, the commercialization of five new kits for cytokine measurement interleukin ((IL)-1, IL-6, IL-8, tumor necrosis factor (TNF)-α and IL-2R) on an automated immunoanalyzer, the Immulite®, seems to be a new approach for the determination of these markers. We report here the evaluation of the performance of these tests. The technique is based on a solid phase (bead) two site chemiluminescent enzyme immunometric assay. The analysis is performed within 60 to 90 minutes and the calibration is stable for 15 days.
The values of the between-run imprecision study were similar to those from the within-run study with coefficients of variation (CV) ranging from 2% (low values of IL-8) to 11.5 % for intermediate concentrations of IL-6 (500 pg/ml). CVs were usually around 5%.
The accuracy was determined by a linearity study using standards (except for IL-2R) provided by the National Institute for Biological Standards and Control (NIBSC). Slopes obtained during this study were close to 1 (r2 = 0.99), except for IL-6, for which the slope was 1.55. TNF-α values were close to those expected. IL-1 results were about 20 % higher. IL-6 values were over estimated above 100 pg/ml and under estimated below this value. IL-8 study seemed to be impaired by the poor stability of this molecule in the NIBSC preparation. Correlation study with standard laboratory techniques gave variable results : for IL-1 (n = 43) the slope was 0.77 (study carried out using cell culture media), for IL-6 (n = 54) the slope was 0.78, for IL-8 (n = 37) the slope was 1.64, for TNF-α (n = 40) the slope was 0.33 and the slope for IL-2R (n = 51) was 5.1. For the last cytokine, the unit in Immulite assay was different from the one used in our comparison technique. Cross-calibration results were consistent with these data and show that the bias is probably linked to a calibration problem.
The study demonstrated excellent practicality of the system, and good stability of the calibration curve (15 days). However, the sample volume required (350 μl for the IL-6 and the TNF-α) could constitute a limitation for pediatric measurements.
Copyright (c)1999 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Metrological Support of the Institute for Reference Materials and Measurements (IRMM) to Clinical Chemistry
- Web Applications for Total Quality Management
- Inflammation, the Acute Phase Response and Atherosclerosis
- Characterization of Two Distinct Mechanisms for Induction of Apoptosis in Human Vascular Endothelial Cells
- Lipid Peroxidation and Antioxidant Defenses in Cystic Fibrosis Patients
- Autoantibodies against Oxidised Low-Density Lipoprotein in Patients with Obstructive Sleep Apnoea
- Inter-α-Inhibitor (IαI) Concentration in Pig Plasma Is Independent of Acute-Phase Protein Response
- Advances in Reverse Transcription Polymerase Chain Reaction Analysis of Cellular mRNA Levels of Transforming Growth Factor-β1 by Capillary Electrophoresis with Laser-Induced Fluorescence Detection
- Determination of Ascorbic Acid in Plasma and Urine by High Performance Liquid Chromatography with Ultraviolet Detection
- A New Liquid Homogeneous Assay for the Determination of HDL-Cholesterol
- On the Standardization of Total Prostate-Specific Antigen: an Exercise with Two Reference Preparations
- Analytical Quality Specifications for Serum Lactate Dehydrogenase Isoenzyme 1 Based on Clinical Goals
- Physiological HEPES Buffer Proposed as a Calibrator for pH Measurement in Human Blood
- Towards Common Reference Intervals in Clinical Chemistry
- Evaluation of an Automated Method for Cytokine Measurement Using the Immulite® Immunoassay System
- Handbook of Interpretation of Diagnostic Tests by Jacques Wallach
- Assessment of a Major Academic Development Programme Linking European Union with Central and Eastern Europe
