The immuassay handbook parte59


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The immuassay handbook parte59

  1. 1. 567© 2013 David G. Wild. Published by Elsevier Ltd. All rights reserved. The ADVIA Centaur XP is a fully automated random- access immunoassay system, using chemiluminescent trac- ers and paramagnetic particle solid-phase reagents. The system uses common reagents with the ADVIA Centaur and ADVIA Centaur CP immunoassay systems from Sie- mens Healthcare Diagnostics. The ADVIA Centaur fam- ily of analyzers provide an extensive assay menu that includes fully automated infectious disease testing. The system is a stand-alone floor model that includes a refrigeration unit holding up to 30 assay packs onboard. First introduced in March 1998, the ADVIA Centaur was the first of a new generation of immunoassay systems. Since that time, ADVIA Centaur instruments were expanded and improved with subsequent instrument launches. ADVIA Centaur CP was launched in 2005 and delivered the same technology and assay menu in a smaller benchtop analyzer. ADVIA Centaur XP was launched in 2006, which significantly enhanced the productivity and efficiency of the ADVIA Centaur analyzer. Today’s ADVIA Centaur portfolio provides immunoassay testing solutions for small sized laboratories to very large laboratories. The ADVIA Centaur XP has a user-friendly graphical interface that is easy to use in global markets. To allow for high system productivity, all system supplies can be changed during operation, without any need to pause or stop processing. The ADVIA Centaur may be easily inte- grated into a fully automated laboratory with a sample transport system (see Fig. 1). Typical Assay Protocol Assays are performed on the ADVIA Centaur using multiple architectures to obtain the most reliable results. All the steps are performed automatically, with the operator required only to load samples and reagents. Each assay is performed in a discrete disposable plastic cuvette, which travels in an incuba- tion ring that indexes every 15s. The bidirectional incubation ring has the flexibility to support a wide variety of assay pro- tocols. Incubation times vary per assay with a minimum of up to 8min. During processing, sample is dispensed, reagents are added and separation of free from bound tracer is achieved by magnetic separation of the micron-sized paramagnetic particle solid-phase reagent and bound tracer in the cuvette. This reaction is measured by a luminometer component after the tracer is oxidized, yielding a light flash that is concentra- tion dependent. The first result is reported in 18min for most of the assays, each subsequent result in 15 second intervals. For the layout of the system components, see Fig. 2. Product Features G The ADVIA Centaur XP can perform up to 240 tests per hour with 840 tests of walkaway time. The system holds 180 samples when fully loaded. G Reagents, samples, and supplies may be loaded on the system at any time, without pausing. G The ADVIA Centaur requires no daily start-up. Due to the onboard refrigeration, 30 assay packs may be stored onboard. Average onboard stability is 28 days. G The system has autodilution, repeat, and cascade reflexing capabilities. The samples will be held in the in-process queue if repeat tests or dilution are required, the operator does not have to find the samples and reload them. G The ADVIA Centaur was designed with a dedicated STAT port, where STATs may be added to the system at any time and will be analyzed immediately without interruption to routine testing. G The ADVIA Centaur uses disposable sample tips for every test, eliminating all sample-to-sample carryover and the need to wash sample probes. The system has clot detection and management capabilities. G Primary sample tubes may be used on the system, elim- inating the need for pouring off serum into sample cups. Bar-coded samples may be utilized for positive sample identification by the system, and several bar code formats are recognized, including Code 39, Coda- bar, Code 128, and Interleaved 2 of 5. G The daily maintenance consists of an automated clean- ing procedure. Weekly and monthly maintenance requires minimal hands-on time. G Bidirectional interfacing to a laboratory information system is easily accomplished, allowing downloading of information, operation in host query mode, and upload- ing of test results. G The ADVIA Centaur XP is capable of directly interfac- ing with laboratory automation systems without addi- tional robotics. The sample probe has the flexibility to ADVIA Centaur® XP Jean Metzar ( C H A P T E R 7.10 FIGURE 1 The ADVIA Centaur XP system (The color version of this figure may be viewed at
  2. 2. 568 The Immunoassay Handbook sample directly from an automated track to the ADVIA Centaur XP, making the system efficient for managing workflow requirements. Assay Principle Assay protocols, which are stored in memory, utilize com- petitive binding, immunometric (sandwich) principles, anti- gen bridging, and µ-capture depending on the specific assay. The system can perform one-step, extended one- step, two-step, and extended two-step incubation protocols. Quantification of results is achieved by oxidation of the acridinium ester (AE) tracer reagent, followed by detection and quantification of the resultant intense quick flash emis- sion. Assays are performed in discrete disposable cuvettes, which may be loaded and replenished randomly at any time. The AE-based chemiluminescence methodology fea- tured in ADVIA Centaur XP has always been a state-of- the-art methodology but is also a dynamic technology undergoing continuing evolution and innovation. Ongo- ing research has allowed continuing development of next- generation assays that meet or exceed the evolving demand for improved performance in various clinical applications. Key to these adaptations is the fact that the AE technology is based on a family of chemiluminescent structures that can be selectively optimized for individual assays. These ongoing modifications provide opportunities for improved detection and precision. An example of an immunometric ADVIA Centaur XP assay principle is shown in Fig. 3. AE Enhancement Features G High quantum yield. High signal-to-noise ratio enhances sensitivity and low-end precision. G Hydrophilicity. Improves efficacy of the wash step, yielding low nonspecific binding. G Hydrolytic stability. Yields long reagent shelf life and extended onboard stability. G Versatility. Suitable for labeling small haptens, large antigens, antibodies—supporting an extensive assay menu. G Small size. Analytes directly labeled with AE differ minimally from native analyte. G Simplicity. Uncomplicated mechanism for light trig- gering with hydrogen peroxide and base. G Rapid kinetics. Light emission complete in 1–5s, allow- ing high throughput. Calibration ADVIA Centaur XP assays are calibrated using a stored, lot-specific, or fixed master curve of up to 10 concentra- tion points, depending on the assay. The curves are 1 Primary reagent compartment 12 Ancillary probe 2 Primary reagent probes 13 Sample probe 3 Incubation ring 14 Ancillary reagent queue 4 Luminometer 15 Sample tip tray 5 Base probe 16 Inprocess queue 6 Waste probe 17 Sample entry queue 7 Cuvette loading bin 18 Sample rack 8 Aspirate probes 19 Stat entry 9 Magnets 20 Sample exit queue 10 Wash block 21 User Interface workstation 11 Acid probe FIGURE 2 ADVIA Centaur XP system—top view (The color version of this figure may be viewed at
  3. 3. 569CHAPTER 7.10 ADVIA Centaur® XP established by the Quality Control Laboratory at Siemens Healthcare Diagnostics. These master curves are supplied on a bar-coded card for rapid and accurate entry into the memory of the ADVIA Centaur XP user interface. The master curve is then used by the software to quantify each assay performed with that lot of reagents. Calibration eval- uation ranges, which include slope, ratio, low, and high calibrator deviation and precision, ensure a valid calibra- tion. Periodic recalibration is accomplished by inclusion of a set of two calibrators. Recalibration intervals vary depending on the assay and are tracked and controlled by onboard software. Multiple master curves may be stored in system memory for each assay, simplifying lot to lot switching. Raw data (relative light units) for control and patient data are retained by the system when a valid cali- bration is not present for the specified assay and can be quantified as soon as the calibration is valid. Antibodies A combination of polyclonal and mouse monoclonal anti- bodies is used in many ADVIA Centaur assays. In immu- nometric assays, this multispecies technology minimizes the risk of aberrant results due to heterophilic binding by human anti-mouse antibodies (HAMA), which can occur in dual mouse monoclonal assays. Where dual mouse monoclonal antibodies are utilized, blocking reagents are added to minimize the risk of HAMA effects. Separation The solid-phase reagents used in the ADVIA Centaur assays are suspensions of micron sized, specially coated fer- ric oxide particles. These particles are small enough to pro- vide extremely high surface area for rapid binding kinetics and stay in suspension for prolonged periods but are rapidly and cleanly separated through their paramagnetic attrac- tion when placed in a magnetic field. The ADVIA Centaur refrigerated reagent compartment gently rocks the reagent packs at periodic intervals. The reagents are packaged in a Ready-Pack® that contains an S-shaped flow design for optimal resuspension of the particles. The Parafilm®-like coating covers the pack openings that are punctured during reagent probe aspiration. Individual assay packs provide sufficient volume for 50–200 tests (see Fig. 4). After dispensing the sample, tracer and solid-phase reagents into the test cuvette, and completion of the incuba- tion period, the particles are magnetically pulled to the flat wall of the cuvette by magnets mounted on the back of a ring within the incubation chamber. This separate ring allows the FIGURE 3 Example of ADVIA Centaur XP assay principle (immunometric type).
  4. 4. 570 The Immunoassay Handbook magnets to move within the ring to any location that they are required. The liquid contents of the cuvette are aspirated, then water or a specially formulated wash solution is injected to resuspend and remove the nonspecific bound tracer. Rese- paration is accomplished automatically in this step. Water is provided from an onboard reservoir (1.5L capacity) fed by a connection to a deionized water supply. A bulk water bottle (9.5L capacity) is available for labs that cannot provide a direct connection. The liquid waste is let away from the system to a laboratory disposal area. A bulk waste container, into which the waste may be emptied while the system is running, is also available for labs that do not have the infrastructure to support direct waste dis- charge. When the system is directly plumbed to water and waste, no operator intervention is required. Signal Generation and Detection Following separation and washing of the solid-phase par- ticles, they are resuspended in an oxidizing reagent at an acid pH, stored onboard (acid reagent). While held in front of a photomultiplier tube detector, a pH adjusting reagent, also stored onboard (base reagent) is injected, causing the dose-related light emission which is quantified over a period of 4s. The acid and base reagents have a bulk bottle and reservoir stored onboard, so that the reagents may be replenished at any time during a run. Data Processing The flash emission, corrected by background subtraction, is directly related to the stored master curve for quantification. Results are calculated and reported as mass concentration and flagged if out of range, based upon operator-controlled reporting formats. The software allows automatic conver- sion to SI units, if desired. Results may be reported individu- ally as completed or collated into patient reports containing all tests performed on a given sample. If desired, the ADVIA Centaur will automatically hold a sample in the in-process queue for repeat, if the initial result is outside an operator-programmed range. An unlimited number of controls can be defined for each analyte and may be tracked through a 90 day history, and results are displayed in a tabular or Levey-Jennings format. QC rules can be set to evaluate system perfor- mance. Monthly summaries are also accessible for a period of 12 months. Results from 25,000 tests are stored in a cur- rent or historical worklist view. User Interface The user interface of the ADVIA Centaur XP is a 19 inch high-resolution LCD touch screen. The use of intuitive icons and full online help throughout the soft- ware makes training and routine operation rapid and simple to master. A built-in high-speed CD-ROM reader allows easy loading of software and test definitions. Step-by-step instructions and graphics for activities such as mainte- nance, system diagnostics, and troubleshooting are available through the help and online procedures in the event log. A remote access feature has been built into the ADVIA Centaur XP to allow Siemens Technical Assistance groups access to pertinent system information via the internet to aid in troubleshooting and provide rapid problem diagnosis. Interfacing to Laboratory Information Systems Bidirectional interfacing to any central laboratory com- puter is achievable for downloading of testing requests, host query options, and uploading of test results, using bar-coded samples. Interfacing software is written in stan- dardized ASTM format for consistency with a wide variety of LIS systems. Additionally, simple software selections may be made to allow direct sampling from the back of the system off an automated track. Operators can still load routine and STAT samples manually at the front of the system without interfering with the track. This flexibility allows the Centaur to easily integrate into totally auto- mated laboratory systems. Further Reading Day, R., Horschke, W., Hallahan, M., Jackson, T. and Williams, J. System design solutions for high volume immunoassay analysis. J. Clin. Ligand Assay 22, 184 (1999). Geyer, S., Moore, S. and Michetti, D. A study of the potential impact of the ACS: Centaur in a hospital core laboratory. Clin. Chem. 44, A57 (1998). Girgensohn, S., Liedtke, R., Balzer, G., Castor, S. and Hauser, M. Performance of the ACS:Centaur high-capacity, random-access immunoassay system. Clin. Lab. 43, 975–983 (1997). Weinzierl, C. Productivity evaluation of random-access immunoassay platforms. Am. Clin. Lab. 16, 4–5 (1997). FIGURE 4 The Ready-Pack®, containing the test reagents (The color version of this figure may be viewed at