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Immunological Tests for Diagnosis of Disease and Identification of Molecules
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Agglutination is an assay based upon the same principles as precipitation, but in it the antigen is a colloidal particle in suspension. Agglutination is widely used for blood typing. Agglutination, like precipitation, occurs in two stages. Antibody first reacts with antigenic determinants that are part of the large structure, such as red cells or bacteria (sensitization), and then forms bridges between antigenic determinants on adjacent cells to yield grossly visible clumps (agglutination). When antibody is in excess, a phenomenon known as the prozone may occur. In blood group work, for example, reactions of high titer antibodies with their antigens may appear to be weak or negative when undiluted serum is used but become strong with diluted serum. This is because while antibody binding does occur outside of the zone of equivalence, a lattice does not form and clumping cannot therefore occur. The process of formation of a lattice during agglutination is similar to the process which occurs in precipitation.
Blood Transfusion
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Agglutination occurs when red blood cells are close enough to allow antibodies to link to adjacent cells. When red cells are suspended in solutions containing free ions, electrical repulsion (zeta potential) between cells occurs as a result of negatively charged surfaces. This may be reduced by the presence of albumin in the medium or enzyme treatment of the red cells with papain, which removes negatively charged carbohydrates (e.g. sialic acid) from the cell surface. The albumin test at 37°C is used to enhance agglutination, usually for IgG antibodies. Papain agglutination increases the titres of cold agglutinins.
The Hematologic System and its Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
Similar to the four major blood groups, blood can be classified on the basis of Rh factor, also called rhesus factor for the rhesus monkey in which the grouping was first discovered. Rhesus factor is a group of antigens that is found on the surface of red blood cells in about 85% of all people. Those who possess the factor are called Rh positive; those whose red blood cells lack the antigens are Rh negative. When an Rh negative person is exposed to Rh positive blood, the individual will develop antibodies to the antigen; on subsequent exposures, the antigen/antibody reaction will cause agglutination.
Strategies to overcome the diagnostic challenges of autoimmune hemolytic anemias
Published in Expert Review of Hematology, 2023
Wilma Barcellini, Bruno Fattizzo
The indirect antiglobulin test (IAT) reveals the presence of auto- or alloantibodies in patient’s serum [1,19]. The serum is incubated with standardized red blood cells panels of known antigenicity, and then anti-human globulin is added. A positive test (revealed by agglutination) identifies the antigenic specificity of the antibody. The IAT test is used in prenatal testing of pregnant women, in testing prior to a blood transfusion, and in the identification of alloantibodies in recently transfused patients. In AIHA, it may be positive, allowing the characterization of the antigen specificity (not strictly necessary for the diagnosis), usually the Rh system in wAIHA and the I/i erythrocyte antigens in CAD [1]. In the latter, it is important to perform the titer of cold agglutinins in serum, since a value less than 64 is considered associated with secondary forms of cold AIHAs, while a greater titer is generally required to confirm the diagnosis of CAD [2,4,25].
Overcoming challenges in the diagnosis and treatment of parasitic infectious diseases in migrants
Published in Expert Review of Anti-infective Therapy, 2020
Francesca F. Norman, Belen Comeche, Sandra Chamorro, Rogelio López-Vélez
Specific circulating anti-Leishmania antibodies are detectable in almost any immunocompetent individual with clinical VL but have a limited role in immunocompromised individuals. Serology may remain positive for many months after treatment and is therefore not useful for monitoring response to treatment and also has no use in cases of CL [78]. The most used quantitative serologic methods are direct agglutination tests, ELISA-based methods, and indirect immunofluorescence. The immunochromatographic strip using the rK39 antigen-RDT is a rapid qualitative diagnostic test which may be especially useful in migrants with infections acquired in specific geographical regions (97% sensitivity in the Indian subcontinent, 85% in east Africa, and 83% in the Mediterranean and Latin America) [86,87].
ABSTRACT
Published in Acta Clinica Belgica, 2018
L. Musger, V. Matheeussen, K. Loens, H. Goossens
Initial investigations included a blood differential performed on EDTA blood with both a liver and kidney functions assessment and an initial infectious serological screening performed on a serum collected on admission day. A Leptospira IgM rapid immunochromatographic test (Leptocheck, Zephyr Biomedicals) was performed on a serum specimen collected 5 days post-symptom onset. In addition, a Microscopic Agglutination Test (MAT) was carried out. Serum was brought into contact with 10 cultures of different Leptospira serotypes. Specific antibodies, present in the sample, will agglutinate and partly lyse the Leptospira. One drop of suspension was brought onto a slide and interpretation was done by dark field microscopy. All serological tests were performed at the Institute of Tropical Medicine (Antwerp, Belgium). Also, in CODA/CERVA laboratory, DNA was extracted from the same sample and challenged to a TaqMan PCR targeting the Hap1/LipL32 gene (diagnostic PCR). Positive PCR samples were further tested by lfb1 mono-gene targeted PCR for genotyping as previously described (3).