Bead-Based Immunoassay Techniques Quiz

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.

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.