Agglutination inhibition

Agglutination inhibition

• 1.
  AGGLUTINATION INHIBITION
• 2.
  A modification ofthe agglutination reaction, called agglutination inhibition, provides a highly sensitive assay for small quantities of an antigen. For example, one of the early types of home pregnancy test kits included latex particles coated with human chorionic gonadotropin (HCG) and antibody to HCG.  The addition of urine from a pregnant woman, which contained HCG, inhibited agglutination of the latex particles when the anti-HCG antibody was added; thus the absence of agglutination indicated pregnancy. Agglutination inhibition assays can also be used to determine whether an individual is using certain types of illegal drugs, such as cocaine or heroin.
• 3.
  The original homepregnancy test kit employed hapten inhibition to determine the presence or absence of human chorionic gonadotropin (HCG). The original test kits used the presence or absence of visible clumping to determine whether HCG was present. If a woman was not pregnant, her urine would not contain HCG; in this case, the anti-HCG antibodies and HCG-carrier conjugate in the No visible clumping kit would react, producing visible clumping. If a woman was pregnant, the HCG in her urine would bind to the anti-HCG antibodies, thus inhibiting the subsequent binding of the antibody to the HCG-carrier conjugate. Because of this inhibition, no visible clumping occurred if a woman was pregnant.
• 4.
  Agglutination inhibition assaysare widely used in clinical laboratories to determine whether an individual has been exposed to certain types of viruses that cause agglutination of red blood cells. If an individual's serum contains specific antiviral antibodies, then the antibodies will bind to the virus and interfere with hemagglutination by the virus. This technique is commonly used in premarital testing to determine the immune status of women with respect to rubella virus. The reciprocal of the last serum dilution to show inhibition of rubella hemagglutination is the titre of the serum. A titre greater than 10 (1:10 dilution) indicates that a woman is immune to rubella, whereas a titre of less than 10 is indicative of a lack of immunity and the need for immunization with the rubella vaccine
• 6.
  APPLICATIONS Agglutination test iswidely applicable in the field of Clinical Microbiology Blood typing of recipient and donor at the time of blood transfusion. Helps in the detection of antibody presence and to quantify the amount of antibody present in the patient’s blood. Active agglutination helps in serodiagnosis of Toxoplasmosis, brucellosis etc. Passive agglutination helps in the determination of the Rh-factor Widely used in techniques like latex and hemagglutination. Helps to detect the type of antigen and to quantify the amount of antigen present in the patient’s blood.