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34 Cards in this Set

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Purpose of Bleeding Time
Screen for defects of PRIMARY hemostasis. Measures in vivo plt function
Normal range for BT
1-9 Minutes
Causes of FALSELY increased BT
aspirin
other drugs that inhibit plt fctn
Conditions assoc with increased BT
Thrombocytopenia, Platelet dysfunction, vascular abnormalities, vWF disease, Bernard-Soulier,
Glanzmann's thrombasthenia, Congenital storage pool disease, Afibrinogenemia, Ehlers-Danlos syndrome, Uremia
Principle of Platelet Function Analysis
Test cartriges w/ membranes coated w/ platelet agonists
-whole blood aspirated under controlled flow cond thru an aperture in membrane
-Plts undergo AAA on membrane surrounding aperture
-time req for plt plug to occulude aperture indicates plt function
Purpose of Platelet Function Analysis
Reliable, cost-effective
-easier than plt aggregometry
Principle of Platelet Aggregation
-PRP measured photometrically
-aggreg agent added, plts clump, % transmittance directly prop to amt clumping in plts
-Aggreg. agents: ADP, collagen, ristocetin, epinep., arachidonic acid
What are the primary and secondary waves in the platelet aggregation test?
1=direct response of plts to aggregating reagent (shape change)
2=complete aggregation (endogenous ADP release from plt dense bodies)
What's special about using ristocetin in platelet aggregometry?
it's action is dependent on interaction of vWF & GPIb/IX. Represents plt agglutination, not aggregation
Purpose of PT Test
-mainly monitor oral anticoag therapy
-screen for inherited EXTRINSIC or COMMON pathway deficiencies
-acquired factor deficiencies
Principle of PT Test
-Plasma re-Ca in presence of excess tissue factor & time for clot formation is measured
-Test bypasses intrinsic factors
-unaffected by plts (because FIII has phospholipids)
What is the normal range for PT test? and what caveat is there?
~10-14 sec
varies from lab to lab because of different techs, reagents, populations, equipment...
Causes for elevated PT
oral anticoag therapy
vitamin K deficiency
Liver disease (acquired cond)
specific coag factor deficiencies
inhibitor
Purpose of APTT
-screen to eval factors in INTRINSIC pathway (eval all xcpt VII,XIII,PF3)
-acquired or inherited
-monitor heparin therapy
-detect inhibitors in blood
Principle of APTT
-Ca in blood bound by NaCitrate to prevent coag
-plasma after centrifg contains all intrinsic factors xcpt Ca & plts
-must add: Ca source (CaCl), Phospholipid substitute (PF3), activator (ellagic acid)
normal ranges for APTT
- 30-40 sec
-varies lab to lab
APTT increased in...
INTRINSIC or COMMON pathway deficiencies
heparin therapy (main use)
inhibitors
What does elevated APTT w/ prolonged incubation mean?
Fletcher factor deficiency

-incubating 10 min instead of 4
Purpose & Principle of TT
measures conversion of fibrinogen to fibrin after adding excess thrombin to citrated plasma
-time for clot to form measured
Normal range for TT
10-15 sec
Causes of prolonged TT
Hypofibrinogenemia
Dysfibrinogenemia
Paraproteins (e.g., cryoglobulin)
Presence of heparin
Presence of FDPs
Presence of plasmin
Principle of Quantitative Fibrinogen
ability of thrombin to convert fibrinogen to fibrn
-clotting time of diluted plasma INVERSELY prop to fibrinogen conc
-excess amts thrombin added to diluted plasma & clotting time noted
Normal range for Quant Fibrinogen
200-400 mg/dL
Causes of LOW fibrinogen levels
<200 in children normal!
-hypofibrinogenemia, dysfibrinogenemia
-liver disease
-DIC
-fibrinolysis
Causes of HIGH fibrinogen levels
Remember: Fibrinogen=Acute Phase Reactant
-Pregnancy
-Trauma
-estrogen therapy
Purpose of FXIII screening test
Remember: FXIII changes H-bonds to covalent in clot
-deficiency of FXIII results in unstable clots
-test is time for clot to dissolve in 5M urea. Normal=~24 hrs
Principle of FDP
-latex particles coated w/ Ab to fibrinogen fragments D & E
-positive is agglutination
Purpose of soybean trypsin inhibitor in FDP
prevents In vitro fibrinolysis
Normal range for FDP
10-40 ug/dL
Purpose of D-Dimer
-latex agglut for specific cross-linked fibrin derivatives w/ D-Dimer domain
-eval pts w/ DVT or PE (which have elevated values)
Purpose of mixing studies
differentiate a factor deficiency from the presence of an inhibitor.
Mix pt. plasma w/ normal plasma. If inhibitor, will also inhibit normal factors, thus no correction
What are 2 specific coagulating inhibitors, and what would the results be in mixing studies?
Lupus-like anticoagulant,
Factor VIII inhibitor

-There will be NO CORRECTION after 2 hr incubation
(FVIII inhibitor corrects after immediate, but goes away)
What is the dRVVT
Dilute Russell's Viper Venom Time
-has venom, Ca, LIMITED conc phospholipid
-venom in presence of FV, phospholipid, and Ca will activate FX => prothrmbn to thrombin
-dRVVT ELEVATED w/ lupus anticoagulant
What patients do we see inhibitors?
Chronic illness
FVIII and FIX deficiencies
congenital coag deficiencies
postpartum women