- PFA-100 = citrated whole blood placed in a disposable cartridge containing a membrane coated with collagen/adrenaline or collagen/ADP into which a microscopic aperture has been cut -> with high shear rates contact of blood with the membrane causes platelets to aggregate and occlude the aperture.
- time to occlude the aperture is recorded (closure time)
- very rapid + simple
- has largely replaced the bleeding time.
- subject to a number of variables:
- platelet count
- ABO blood groups
- plasma vWF
- a normal test has a high negative predictive value
CAUSES OF QUALITATIVE PLATELET DYSFUNCTION
- renal failure
- hepatic failure
- drugs: anti-platelets
- autoantibodies (HITTS)
- haematological problems: vWD