blk1 Serological tests and blood stain ppt

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Serological tests
By: Deshanie Govender
Primary serological tests: (Marker techniques) e.g.
1.
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–
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Classification of antigenEnzyme linked immuono sorben assay (ELISA)
antibody
interactions:
Immuno flurescent antibody technique (IFAT)
Radio immuno assay (RIA)
Secondary serological tests: e.g.
2.
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Agglutination tests
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Complement fixation tests (CFT)
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Precipitation tests
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Serum neutralization tests (SNT)
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Toxin-antitoxin test
Agglutination tests:
1. Agglutination/Hemagglutination
The reaction of an antibody with the antigen can be detected
by agglutination (clumping) of the antigen. The general term
agglutinin is used to describe antibodies that agglutinate
antigens. When the antigen is an erythrocyte the term
heamagglutination is used.
a. Qualitative agglutination test
Agglutination tests can be used in a qualitative manner to
evaluate for the presence of an antigen or an antibody. The
antibody is mixed with the particulate antigen and a positive
test is indicated by the agglutination of the particulate
antigen.
For example, a patient's red blood cells can be mixed with antibody to a
blood group antigen to determine a person's blood type. In a second
example, a patient's serum is mixed with red blood cells of a known
blood type to assay for the presence of antibodies to that blood type
in the patient's serum.
b. Quantitative agglutination test
Agglutination tests can also be used to measure the level of
antibodies to particulate antigens. In this test, serial dilutions are
made of a sample to be tested for antibody and then a fixed number
of red blood cells or bacteria or other such particulate antigen is
added.
2-Passive hemagglutination:
The agglutination test only works with particulate antigens.
However, it is possible to coat erythrocytes with a soluble antigen
and use the coated red blood cells in an agglutination test for
antibody to the soluble antigen. This is called passive
hemagglutination.
The test is performed just like the agglutination test. Applications
include detection of antibodies to soluble antigens and detection of
antibodies to viral antigens.
Blood Spatter
Blood Spatter = 2 or
more droplets of blood
used to reconstruct a
series of events
surrounding a violent
event.
BSA can determine
Mechanism that created the stains
Direction a blood droplet was traveling
Point/Area of origin
Type of object used in attack
Minimum number of blows
Positioning of the victim, suspect and
objects during events
Sequence of events
ANGLE OF IMPACT
1) Passive Drops
EXTRA ROUGH SURFACE
SMOOTH SURFACE
ROUGH SURFACE
Low Velocity Impact
(LVI)
Blood Spatter size: large (4 mm +)
Impact velocity: up. to 5 feet/sec
Example cause: gravity
Medium Velocity Impact
(MVI)
B.S. size: Medium (1 - 4 mm)
Impact velocity (5 to. 25 feet/sec)
Example cause: car accident / blunt force trauma
High Velocity Impact
(HVI)
B.S. size: (1 mm or smaller) Mist like appearance.
Impact velocity: 100 feet/sec and greater.
Example cause: gunshot
Arterial Spurting
Bloodstain pattern(s) resulting from blood exiting the body under
pressure from a breached artery
Determining angles of
impact
Angle of impact
= direction
blood drop(s) was/were
traveling
Blood droplets in freefall have
the shape of a sphere.
Droplets striking surfaces make
it possible to determine the
angle at which the droplet struck
the surface.

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