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10.3 Labelled Immunoassays — Test 1
Q1. Labelled immunoassays improve on simple precipitation/agglutination chiefly by:✓ Using a detectable label to greatly increase sensitivity and allow quantitation
Q2. In an enzyme immunoassay (ELISA), the signal is produced when:✓ The enzyme label converts a substrate into a coloured product
Q3. A direct ELISA uses:✓ A single labelled antibody that binds the antigen
Q4. An indirect ELISA detecting patient antibody uses, in order:✓ Plate-bound antigen → patient antibody → labelled anti-immunoglobulin
Q5. A sandwich ELISA for an antigen requires that the antigen:✓ Has at least two distinct epitopes for capture and detection antibodies
Q6. A competitive immunoassay is especially useful for measuring:✓ Small molecules (haptens) with only one epitope
Q7. Radioimmunoassay (RIA) uses which type of label?✓ A radioisotope
Q8. A fluoroimmunoassay uses a label that:✓ Emits light of a specific wavelength when excited
Q9. Chemiluminescent immunoassays generate signal by:✓ A light-emitting chemical reaction catalysed by the label
Q10. In a competitive ELISA, the signal is:✓ Inversely proportional to the amount of analyte in the sample
Q11. The washing steps in ELISA are important to:✓ Remove unbound reagents and reduce background signal
Q12. A key advantage of enzyme labels over radioactive labels is that they:✓ Avoid radiation hazards and have a long shelf life
Q13. A standard (calibration) curve in a quantitative immunoassay is used to:✓ Convert measured signal into analyte concentration
Q14. The 'hook effect' in a sandwich immunoassay causes falsely low results when:✓ Analyte is in great excess, saturating both antibodies separately
Q15. Enzyme-linked immunospot (ELISpot) is used to:✓ Detect and count individual cells secreting a specific cytokine or antibody
Q16. A secondary (anti-immunoglobulin) antibody is often labelled rather than the primary because it:✓ Amplifies the signal and allows one labelled reagent to be used for many primaries
Q17. Compared with agglutination, ELISA is generally:✓ More sensitive and quantitative
Q18. A capture (sandwich) ELISA improves specificity because:✓ Two antibodies must bind two epitopes of the same antigen
Q19. Which label type is most associated with environmental/safety concerns from radioactive waste?✓ Radioisotope (RIA)
Q20. Match each assay/feature with its description and select the correct option.✓ A-iv, B-i, C-ii, D-iii