Hook effect: Difference between revisions
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==Mechanism== |
==Mechanism== |
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In an [[agglutination (biology)#Agglutination in hematology|agglutination]] test, a person's [[serum (blood)|serum]] (which contains [[antibody|antibodies]]) is added to a [[test tube]], which contains a particular [[antigen]]. If the antibodies agglutinate with the antigen to form [[immune complex]]es, then the test is interpreted as positive. However, if too many antibodies are present that can bind to the antigen, then the antigenic sites are coated by antibodies, and few or no antibodies directed toward the pathogen are able to bind more than one antigenic particle. Since the antibodies do not bridge between antigens, no agglutination occurs. Because no agglutination occurs, the test is interpreted as negative. In this case, the result is a false negative. The zone of relatively high antibody concentrations within which no reaction occurs is called the ''prozone'' or the ''prezone''. {{cn|date=November 2014}} |
In an [[agglutination (biology)#Agglutination in hematology|agglutination]] test, a person's [[serum (blood)|serum]] (which contains [[antibody|antibodies]]) is added to a [[test tube]], which contains a particular [[antigen]]. If the antibodies agglutinate with the antigen to form [[immune complex]]es, then the test is interpreted as positive. However, if too many antibodies are present that can bind to the antigen, then the antigenic sites are coated by antibodies, and few or no antibodies directed toward the pathogen are able to bind more than one antigenic particle. Since the antibodies do not bridge between antigens, no agglutination occurs. Because no agglutination occurs, the test is interpreted as negative. In this case, the result is a false negative. The zone of relatively high antibody concentrations within which no reaction occurs is called the ''prozone'' <ref>{{Cite journal|title = Assessment of the prozone effect in malaria rapid diagnostic tests|url = http://www.malariajournal.com/content/8/1/271|journal = Malaria Journal|date = 2009-11-30|pmc = 2789093|pmid = 19948018|volume = 8|issue = 1|doi = 10.1186/1475-2875-8-271|language = En|first = Philippe|last = Gillet|first2 = Marcella|last2 = Mori|first3 = Marjan Van|last3 = Esbroeck|first4 = Jef|last4 = Ende|first5 = Jan|last5 = Jacobs}}</ref> or the ''prezone''. {{cn|date=November 2014}} |
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Examples include high levels of [[syphilis]] antibodies in [[HIV]] patients or high levels of cryptococcal antigen leading to false negative tests in undiluted samples.<ref name="pmid7832818">{{cite journal |author=Jurado RL, Campbell J, Martin PD |title=Prozone phenomenon in secondary syphilis. Has its time arrived? |journal=Arch. Intern. Med. |volume=153 |issue=21 |pages=2496–8 |date=November 1993 |pmid=7832818 |doi= 10.1001/archinte.153.21.2496|url=}}</ref><ref name="pmid6997519">{{cite journal |author=Stamm AM, Polt SS |title=False-negative cryptococcal antigen test |journal=JAMA |volume=244 |issue=12 |pages=1359 |date=September 1980 |pmid=6997519 |doi= 10.1001/jama.244.12.1359|url=}}</ref> This phenomenon is also seen in serological tests for Brucellosis. The serological test is mainly seen in the precipitation reaction. The antibody that fails to react is known as the blocking antibody which does not allow the precipitating antibody to bind to the antigens for proper precipitation reaction to take place; but when diluting the serum, the blocking antibody is also diluted and its concentration decreased for proper precipitation reaction to occur. |
Examples include high levels of [[syphilis]] antibodies in [[HIV]] patients or high levels of cryptococcal antigen leading to false negative tests in undiluted samples.<ref name="pmid7832818">{{cite journal |author=Jurado RL, Campbell J, Martin PD |title=Prozone phenomenon in secondary syphilis. Has its time arrived? |journal=Arch. Intern. Med. |volume=153 |issue=21 |pages=2496–8 |date=November 1993 |pmid=7832818 |doi= 10.1001/archinte.153.21.2496|url=}}</ref><ref name="pmid6997519">{{cite journal |author=Stamm AM, Polt SS |title=False-negative cryptococcal antigen test |journal=JAMA |volume=244 |issue=12 |pages=1359 |date=September 1980 |pmid=6997519 |doi= 10.1001/jama.244.12.1359|url=}}</ref> This phenomenon is also seen in serological tests for Brucellosis. The serological test is mainly seen in the precipitation reaction. The antibody that fails to react is known as the blocking antibody which does not allow the precipitating antibody to bind to the antigens for proper precipitation reaction to take place; but when diluting the serum, the blocking antibody is also diluted and its concentration decreased for proper precipitation reaction to occur.<ref>{{Cite book|title = Interferences in Immunoassays|url = http://www.intechopen.com/books/advances-in-immunoassay-technology/interference-in-immunoassays|publisher = InTech|date = 2012-03-23|doi = 10.5772/35797|language = en|first = Johan|last = Schiettecatte|first2 = Ellen|last2 = Anckaert|first3 = Johan|last3 = Smitz}}</ref> {{cn}} |
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==See also== |
==See also== |
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Revision as of 09:52, 11 February 2016
The hook effect or the prozone effect is a false negative result with certain immunoassays due to very high concentrations of a particular analyte. The hook effect mostly affects one-step immunometric assays.
Mechanism
In an agglutination test, a person's serum (which contains antibodies) is added to a test tube, which contains a particular antigen. If the antibodies agglutinate with the antigen to form immune complexes, then the test is interpreted as positive. However, if too many antibodies are present that can bind to the antigen, then the antigenic sites are coated by antibodies, and few or no antibodies directed toward the pathogen are able to bind more than one antigenic particle. Since the antibodies do not bridge between antigens, no agglutination occurs. Because no agglutination occurs, the test is interpreted as negative. In this case, the result is a false negative. The zone of relatively high antibody concentrations within which no reaction occurs is called the prozone [1] or the prezone. [citation needed]
Examples include high levels of syphilis antibodies in HIV patients or high levels of cryptococcal antigen leading to false negative tests in undiluted samples.[2][3] This phenomenon is also seen in serological tests for Brucellosis. The serological test is mainly seen in the precipitation reaction. The antibody that fails to react is known as the blocking antibody which does not allow the precipitating antibody to bind to the antigens for proper precipitation reaction to take place; but when diluting the serum, the blocking antibody is also diluted and its concentration decreased for proper precipitation reaction to occur.[4] [citation needed]
See also
References
- ^ Gillet, Philippe; Mori, Marcella; Esbroeck, Marjan Van; Ende, Jef; Jacobs, Jan (2009-11-30). "Assessment of the prozone effect in malaria rapid diagnostic tests". Malaria Journal. 8 (1). doi:10.1186/1475-2875-8-271. PMC 2789093. PMID 19948018.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Jurado RL, Campbell J, Martin PD (November 1993). "Prozone phenomenon in secondary syphilis. Has its time arrived?". Arch. Intern. Med. 153 (21): 2496–8. doi:10.1001/archinte.153.21.2496. PMID 7832818.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Stamm AM, Polt SS (September 1980). "False-negative cryptococcal antigen test". JAMA. 244 (12): 1359. doi:10.1001/jama.244.12.1359. PMID 6997519.
- ^ Schiettecatte, Johan; Anckaert, Ellen; Smitz, Johan (2012-03-23). Interferences in Immunoassays. InTech. doi:10.5772/35797.
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