What types of direct antiglobulin tests (DATs) are commercially available?

Updated: Jun 25, 2020
  • Author: Julie Katz Karp, MD; Chief Editor: Jun Teruya, MD, DSc, FCAP  more...
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Answer

Answer

RBC autoantibodies and alloantibodies are usually IgM or IgG antibodies, occasionally IgA or mixture of each immunoglobulin. Pentameric IgM causes direct agglutination in saline-suspended RBCs. By contrast, IgG antibodies adhere to the corresponding antigens on the RBC membrane, but they do not result in agglutination. RBCs with adherent IgG antibodies can be considered "sensitized."

Based on work by Coombs and others, it was postulated that, if rabbits were injected with human gamma globulin, they would develop antibodies to the foreign protein, so-called antihuman globulin (AHG). After suitable processing, this AHG would react specifically with IgG adhering to RBC membranes, cross-linking the sensitized RBCs and causing agglutination.

Both polyspecific and monospecific AHG is available commercially. Polyspecific AHG contains anti-IgG and anti-C3d. Monospecific AHG contains either a monospecific anti-IgG or an anti-C3 containing anti-C3d activity. Positive direct antiglobulin test results with a polyspecific AHG should be tested further with monospecific reagents. This additional testing provides further information in determining the type of immune hemolytic anemia involved. [3]


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