blood 1.2

Plasma sample color of tube

Purple/pink

Plasma sample anticoagulant present and how it works

EDTA

• chelates calcium which prevents activation of complement pathway

Plasma sample: presence or absence of complement in sample

Absence of complement

Serum sample: color of tube

Red top

Serum sample: anticoagulant present or not

No anticoagulant

Serum sample: presence or absence of complement pathway

Presence of complement

How to correctly read a blood bank test

Look for hemolysis first (positive reaction)

Face cell button toward you and tilt tube horizontally to observe cells

• if button falls smoothly and slow = probably negative

• If button falls off in clump(s) = agglutination

Grading system to interpret Ag-Ab reactions

Positive reaction “incompatible”

• antigens and corresponding Ab present and form lattice

Negative reaction “compatible”

• corresponding Ag and Ab not present

Grading #s on slides