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Questions and Answers
Which concentration unit is used for the analyte GH (baseline)?
Which detection technology is used in the Vitros 250 analyzer?
Which company offers the Cobas 8000 analyzer?
Which type of assay involves phase separation and separation of analytes bound to solid phase from that in solution?
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Which of the following factors can affect the performance of labs in the RCPA EQA scheme?
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What type of bias is apparent in the lab's results compared to the median results from other labs?
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What type of distribution does the data for all labs show and why?
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What is the analytical principle of the assay specified by the lab for measurement of prolactin?
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Which type of assay uses an excess of antibodies and is typically used for higher molecular weight antigens?
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Which one of the following best describes the allowable limits of performance?
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Which type of assay involves a fixed amount of enzyme-labeled antigen competing with antigen from the patient sample for binding to a limited amount of antibody?
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If a laboratory can measure plasma sodium with a standard deviation (SD) of 3.0 mmol/L, is that considered satisfactory?
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Which type of assay offers higher sensitivity compared to measuring absorbance and involves measuring either a fluorescence signal or chemiluminescence?
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What type of auto-analyzer would be required to measure a steroid present at a concentration of 12 pmol/L?
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Which type of assay uses luminescent labels that emit a photon of light and offers highly sensitive detection with no background light?
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Which type of assay is the Abbott Architect Immunoassay (Chemiflex system)?
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What is the purpose of the wash steps in heterogenous assays?
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Which type of assay is the Roche Immunochemiluminometric assay (ELECSYS system)?
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What is the purpose of the streptavidin coated magnetized beads in the Roche Immunochemiluminometric assay (ELECSYS system)?
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According to the text, what is the principle difference between two-step assays and one-step assays in immunoassays?
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According to the text, what is the purpose of a proficiency program in laboratory testing?
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According to the text, what type of auto-analyzer is required to measure a steroid at a concentration of 12 pmol/L?
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According to the text, what are the two major types of auto-analyzers in a clinical biochemistry laboratory?
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Which term describes assays that can be done entirely in the liquid phase, with no requirement to separate any component of the reagents to get a readout?
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What are the similarities and differences between Siemens Immulite and Roche Elecsys immunoassays?
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What are the two major sources of interference that the Roche Elecsys system is subject to, which are not seen in most other sensitive immunometric assays?
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What is the difference between chemiluminescence and fluorescence, and why do immunoassays using chemiluminescence yield a higher sensitivity?
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Study Notes
Concentration Units and Detection Technologies
- The analyte GH (baseline) is measured in concentration units of μIU/mL.
- The Vitros 250 analyzer uses chemiluminescence detection technology.
- The Cobas 8000 analyzer is offered by Roche.
Assay Types
- Immunosorbent assays (ISAs) involve phase separation and separation of analytes bound to solid phase from that in solution.
- Excess reagent immunoassays use an excess of antibodies and are typically used for higher molecular weight antigens.
- Competitive assays involve a fixed amount of enzyme-labeled antigen competing with antigen from the patient sample for binding to a limited amount of antibody.
Performance and Bias
- Factors that can affect the performance of labs in the RCPA EQA scheme include instrumental, procedural, and reagent variations.
- A positive bias is apparent in the lab's results compared to the median results from other labs, indicating a systematic error.
- The data for all labs shows a non-normal (skewed) distribution, indicating variability in lab performance.
Analytical Principles and Assay Characteristics
- The analytical principle of the assay specified by the lab for measurement of prolactin is immunometric.
- Chemiluminescence assays offer higher sensitivity compared to measuring absorbance and involve measuring either a fluorescence signal or chemiluminescence.
- Chemiluminescence assays use luminescent labels that emit a photon of light and offer highly sensitive detection with no background light.
Assay Systems and Instruments
- The Abbott Architect Immunoassay (Chemiflex system) is a type of heterogeneous assay.
- The Roche Immunochemiluminometric assay (ELECSYS system) is a type of heterogeneous assay.
- The wash steps in heterogeneous assays are necessary to remove excess reagents and minimize non-specific binding.
- The streptavidin coated magnetized beads in the Roche Immunochemiluminometric assay (ELECSYS system) are used to capture the analyte-antibody complex.
Proficiency Programs and Auto-analyzers
- The purpose of a proficiency program in laboratory testing is to ensure accuracy and reliability of laboratory results.
- A proficiency program evaluates laboratory performance by comparing results with peer labs.
- To measure a steroid at a concentration of 12 pmol/L, a high-sensitivity auto-analyzer is required.
- The two major types of auto-analyzers in a clinical biochemistry laboratory are random-access and batch analyzers.
Immunoassay Characteristics
- Homogeneous assays are those that can be done entirely in the liquid phase, with no requirement to separate any component of the reagents to get a readout.
- Two-step assays involve a separate incubation and washing step, whereas one-step assays do not require a separate washing step.
- The principle difference between two-step assays and one-step assays is the separation of incubation and washing steps.
Interference and Assay Comparison
- The Roche Elecsys system is subject to interference from heterophilic antibodies and rf-F(ab')2, which are not seen in most other sensitive immunometric assays.
- Siemens Immulite and Roche Elecsys immunoassays share similarities in their use of chemiluminescence detection, but differ in their assay design and reagent composition.
- Chemiluminescence assays yield a higher sensitivity than fluorescence assays due to the ability to detect single photon events.
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Description
Test your knowledge on bead-based immunoassay techniques with this quiz! Learn about the different assay characteristics, including sandwich assays, chemiluminescent reporter systems, and enzyme-linked immunoassays. Challenge yourself and expand your understanding of immunoassay methods.
