coagulation studies Flashcards
(30 cards)
prothrombin time
tests common and extrinsic pathways
usually calculated into INR
clinical relevance of PT/INR
increased in:
vitamin K deficiency
impaired coagulation factor production eg. liver cirrhosis
factor VII deficiency
DIC
used for monitoring of fit K antagonist therapy eg. warfarin
activated partial thromboplastin time
PTT/aPTT
tests common and intrinsic pathways
common pathway analyses
Factor X and cofactor V, thrombin, fibrinogen
extrinsic pathway analyses
factor VII
intrinsic pathway analyses
Factors XII, XI, IX, and VIII
aPTT/PTT may be prolonged in cases of
Hemophilia
Vitamin K deficiency
DIC
Possibly in von Willebrand disease (Severe cases of vWD can cause factor VIII deficiency, which leads to an impaired intrinsic pathway.)
SLE (if lupus anticoagulant is present)
thrombin time measures
common pathway, but just fibrinogen
clinical relevance of thrombin time
test for fibrinogen deficiency
monitoring of heparin therapy and fibrinolytic therapy
Anti-factor Xa assay
used to monitor certain anticoagulant therapies
Low molecular weight heparin (LMWH) or fondaparinux therapy in patients with impaired renal function
Unfractionated heparin (UFH) therapy if aPTT is inconclusive (e.g., due to coagulation factor deficiency or heparin antibodies)
D-dimer
fibrin degradation product that correlates with activity of coagulation and fibrinolysis
High sensitivity: Increased serum D-dimer levels occur in deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation.
Low specificity: Elevation can also occur due to other conditions, including malignancies, infection, pregnancy, renal insufficiency, or surgical procedures.
Ristocetin cofactor assay
measures the ability of von Willebrand factor (vWF) to agglutinate platelets
If ristocetin is added to blood lacking vWF (or the vWF receptor), platelets will not aggregate.
Von Willebrand disease
(↓ vWF)
Failure of platelet aggregation or a ristocetin cofactor level < 30 IU/dL that corrects with the addition of normal plasma
Bernard-Soulier syndrome
(↓ vWF receptor on platelets)
Failure of platelet aggregation or a ristocetin cofactor level < 30 IU/dL that does not correct with the addition of normal plasma
Glanzmann thrombasthenia
Normal platelet aggregation in response to ristocetin
Failure of platelet aggregation in response to other agonists such as ADP, epinephrine, collagen, and thrombin
haemophilia A
factor VIII, most common
hemophilia B
factor IX
hemophilia C
factor XI
hemophilia manifests on coat studies as
increased PTT
What is hemarthrosis?
Bleeding into joints
What are the common symptoms of hemophilia?
Hemarthrosis and muscular or soft tissue hematomas
These symptoms may vary based on the severity of the condition.
What long-term complication can result from repeated hemarthrosis?
Joint destruction
This is a serious concern for individuals with hemophilia.
What is the treatment for severe hemophilia?
Prophylactic substitution of clotting factors
What treatment can be used for mild hemophilia A?
Desmopressin
Desmopressin is a synthetic vasopressin analog that can help increase clotting factor levels.
