platelet testing Flashcards
capillary fragility test- tourniquet test
BP cuff inflated for 5 mins
observe arm for petechiae
>5 petechiae in 5cm area = increased
increased vessel permeablility
decreased plt count
ab plt fx
capillary fragility test
blood passed thru glass bead column (mimics exposed collagen) plt count determined
normal 31-83%
bleeding time
evaluates plt # and fx
standardized cut made on forearm- time for clotting determined
normal BT
3-9 mins
clot retraction
evaluates plt # and fx
1 ml plasma clotted; after 1 hr expressed serum measured
normal clot retraction
0.76-0.9ml
platelet aggregation
evaluates plt fx: ability to aggregate when exposed to agonists (in vivo ADP/collagen)
platelet aggregation procedure
plt rich plasma set to 0% transmittance
plt poor plasma set to 100%
agonists added to plt rich plasma (patient) and light transmittance graphed
as plt aggregate % transmittance increased
single wave normal platelet aggregation
arachadonic acide
high concentration of ADP
thrombin
collagen
ristocetin
double wave normal platelet aggregation
ADP
epinephrine
PFA 100
measures plt fx
instrument:
blood passes thru membrane; plt adhere; thrombus stops blood flow
times how long to block plug
on the PFA 100 what is the closure time dependent on?
VWF
hct
plt count
plt fx
plt fx testing interference; PFA 100
hemolysis
lipids
spices (ginger, garlic, vitamins)
microthrombi
bubbles in system
Prothrombin consumption test
evaluates PF3 availability
measures consumption of factor 2
prothrombin consumption test procedure
serum used
serum missing 1, 2, 5, 8
thromboplastin has added 1, 5, leaving 2 the only variable
