NATURE OF BLOOD AND BLOOD GROUPING
There are 19 known blood group systems encompassing over 200 antigens. Only two of these, however, (the ABO and the Rh) can commonly cause haemolytic transfusion reaction (HTR) as well as haemolytic disease of the newborn (HDN). Several other systems (Kell, Duffy, Kidd) can occasionally determine HTR and HDN. Two other systems (P and MN) very rarely cause HTR and HDN and the Lutheran and Lewis systems rarely cause HTR but not HDN. Current understanding of the serology and genetics of the major blood group antigens has enabled prevention of both HTR and HDN and this understanding forms the topic of this lecture. TEST FOR BLOOD(SCREENING AND CONFIRMATORY)
Many different tests have been used to confirm that a stain contains blood. The oldest is chemical confirmation of the presence of hemoglobin or its derivatives by the formation of specific crystals. For example, the Takayama or hemochromogen test, in which ferrous iron from hemoglobin reacts with pyridine to produce red feathery crystals of pyridine ferroprotoporphyrin. Another confirmatory test uses the Teichman reagent, consisting of a solution of potassium bromide, potassium chloride and potassium iodide in glacial acetic acid, and is heated to react with hemoglobin. The reaction first converts the hemoglobin to hemin, and then the halides react with the hemin to form characteristic brownish-yellow rhomboid crystal BLOOD STAIN CLASSIFICATION AND ITS SUBTYPES
Bloodstain pattern analysis (BPA) is defined as the examination of the shapes, size, locations and distrib ution
patterns of bloodstains, in order to provide an objective analysis of the physical events that gave rise to their origin by application of concepts of biology, biochemistry, physics and mathematics. Not only can these concepts help to define and reco
nstruct events associated in a bloodletting event but also may provide investigative leads/information. They can lead to new information,...
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