Prozone (hook) effect
Definition
A false-negative agglutination result caused by antibody excess. When antibody molecules outnumber antigen sites, each site is occupied by a single antibody that cannot bridge to another particle. No lattice forms and no clump is visible. The effect resolves on dilution, which is why undiluted samples can give apparently negative results that become positive after 1:8 or 1:16 dilution.
Related terms
- Agglutination titre
- The reciprocal of the highest dilution of a serum or antigen solution at which visible agglutination still occurs. A titre of 1:64...
- Antiglobulin (Coombs) test
- A two-stage assay that detects IgG antibodies bound to red blood cells. The direct test detects in-vivo cell-bound IgG; the indirect test...
- Cross-reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Hemagglutination
- Agglutination specifically involving red blood cells as the antigen-bearing particles. Direct hemagglutination occurs when antibodies bind surface antigens naturally present on red...
- HemaTrace ABAcard
- A lateral-flow device from Abacus Diagnostics that uses an anti-human haemoglobin monoclonal antibody. It is the most widely validated immunological blood confirmatory...
- Lateral-flow immunochromatographic assay
- A rapid, single-use immunoassay format in which sample extract migrates along a nitrocellulose membrane past a detection zone loaded with antigen-specific antibody...
- Low-ionic-strength saline (LISS)
- A reaction medium with reduced salt concentration used to enhance agglutination sensitivity, particularly for IgG antibodies. Lowering ionic strength reduces the electrostatic...
- Monoclonal antibody
- An antibody produced from a single B-cell clone, recognising a single specific epitope. In forensic species identification, monoclonal antibodies offer higher specificity...
- Passive (indirect) agglutination
- An agglutination format in which a soluble antigen or antibody is adsorbed or covalently linked to a carrier particle (latex bead, tanned...
- RSID-Blood
- Rapid Stain Identification of Blood, a lateral-flow strip from Independent Forensics that also targets human haemoglobin. Functionally equivalent to HemaTrace in principle;...
Explained in these topics
- Agglutination Reactions: Direct and Indirect MethodsA false-negative agglutination result caused by antibody excess. When antibody molecules outnumber antigen sites, each site is occupied by a single antibody th...
- Immunological Confirmatory Tests for Human BloodA false negative that occurs when antigen concentration is so high that all antibody binding sites are saturated before sandwich complexes can form, preventing...