Lecture 9 - Coagulation testing Flashcards
what sample is used for most coagulation testing
PLASMA (use a citrate/blue tube)
why not use serum
it clots and lacks factors needed for testing
4 venipuncture sample tips
- use plastic syringe and tube
- fresh, clean stick
- do not collect from catheter
- properly fill the tube
__ inhibits coagulation by binding calcium
sodium citrate
ratio of citrate to blood MUST be __ why need to fill it appropriately
1:9
Analysis must be preformed ASAP or
plasma should be frozen within 30mins
After centrifugation what is present in citrated plasma
only coagulation factors and other blood chemicals
(NO WBC, RBC, Platelets, or Ca!)
7 tests for coagulation/hemostatic function
- PT
- PTT
- ACT
- Fibrinogen concentration and TT
- FDPs
- D-dimers
- thromboelastography
__ coagulation model is not what happens in the body but what happens in the tube, important for understanding tests
classic cascade
cats, manatees, dolphins and other exotics lack __
factor 12
__ tests the extrinsic (and common) pathway
PT (prothrombin time or one stage prothrombin time) measures time for clot to form when tissue thromboplastin is added = “extrinsic”
How does PT test the extrinsic pathway
measures time for fibrin clot to form in citrated plasma after adding tissue factor (thromboplastin), Ca, and substitute for platelet = “extrinsic” bc adding things
a __ % deficiency is required before prolognation of PT and PTT
70%
prolonged PT means there is inhibition or deficiency of
factor 7, tissue factor or the common pathway factors
what factors are vitamin K dependent coagulation factors
2, 7, 9, 10
PT can be used to monitor __ therapy
warfarin
PT is the best test for __
vitamin K antagonism or deficiency
__ and __ test the intrinsic (and common) pathway
PTT (activated Partial Thromboplastin Time) and ACT
Which test does NOT have tissue factor/thromboplastin added to tube?
PTT (why it’s “intrinsic”). only add things already in the body like contact activator, Ca, and platelet substitute
PTT and ACT can be used to monitor __ therapy
heparin
artificially prolonged test times can be caused by
- delayed testing
- warm sample
- low plasma citrate ratio (inappropriate filled tube) = erythrocytosis
__ test uses patient’s own clotting factors, Ca and platelet’s, it can be done in the clinic for this reason!
ACT
ACT measures time for fibrin clot to form in __ sample using special tube and patient’s own factors
WHOLE BLOOD (PT and PTT tests are run using citrated plasma)
ACT stands for
activated clotting/coagulation time
