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10.2 Precipitation & Agglutination Techniques — Test 1
Q1. A precipitation reaction occurs when:✓ Soluble antigen and antibody cross-link into an insoluble lattice
Q2. Maximum precipitation occurs at the:✓ Zone of equivalence
Q3. Single radial immunodiffusion (Mancini technique) quantifies antigen by measuring the:✓ Diameter (area) of the precipitin ring
Q4. In the Ouchterlony double-diffusion test, a continuous (fused) line between two antigens indicates:✓ Identity (shared epitopes)
Q5. Immunoelectrophoresis combines:✓ Electrophoretic separation of antigens with immunodiffusion
Q6. Direct agglutination tests use antibody to clump:✓ Particulate antigens such as red cells or bacteria
Q7. Passive (indirect) agglutination detects soluble antigen or antibody by:✓ Coating soluble antigen onto carrier particles (e.g. latex) to allow agglutination
Q8. The prozone phenomenon causes a false-negative agglutination result when:✓ Antibody is in great excess
Q9. The Coombs (antiglobulin) test uses anti-human-globulin to:✓ Agglutinate red cells already coated with antibody/complement
Q10. Haemagglutination inhibition is used to:✓ Detect a virus or antibody by its ability to block red-cell agglutination
Q11. Why is agglutination generally more sensitive than precipitation?✓ Particulate antigens make even small amounts of antibody binding visible as clumps
Q12. A precipitin curve shows reduced precipitation in antibody excess; this region is the:✓ Prozone
Q13. The Widal test is an agglutination test used to support a diagnosis of:✓ Enteric (typhoid) fever
Q14. Rocket immunoelectrophoresis (Laurell) quantifies antigen by measuring:✓ The height of the rocket-shaped precipitin peak
Q15. An advantage of gel-based precipitation methods over tube precipitation is that they:✓ Allow visualisation of distinct precipitin lines and antigen comparisons
Q16. Reverse passive agglutination differs from passive agglutination in that the particles are coated with:✓ Antibody (to detect antigen)
Q17. The endpoint titre in an agglutination test is:✓ The highest serum dilution still showing agglutination
Q18. A limitation of precipitation/agglutination tests compared with labelled immunoassays is that they are:✓ Generally less sensitive and more qualitative/semi-quantitative
Q19. Immunofixation electrophoresis is particularly useful for:✓ Identifying and typing monoclonal proteins (e.g. in myeloma)
Q20. Excess antibody inhibiting precipitation and agglutination reactions is known as the:✓ Prozone effect
Q21. For detecting antigen–antibody complexes, which method is generally more sensitive?✓ Agglutination reaction
Q22. The zone of equivalence in a precipitation reaction occurs when:✓ Antigen and antibody are in optimal proportion
Q23. The cross-linking of particulate antigens by antibody into visible clumps is called:✓ Agglutination
Q24. Slide agglutination tests are used in the diagnosis of:✓ Typhoid, rheumatoid factor and Salmonella (among others)
Q25. The Mancini method is a form of:✓ Single radial immunodiffusion (quantifying antigen by ring diameter)
Q26. The Ouchterlony method is a form of:✓ Passive double immunodiffusion
Q27. Antigen–antibody reactions detected by precipitate formation within an agar gel are called:✓ Immunodiffusion assays
Q28. Identification of ABO blood groups is based on which type of reaction?✓ Agglutination
Q29. Match each technique with its description and select the correct option.✓ A-ii, B-i, C-iv, D-iii