Podcast
Questions and Answers
What is the angle at which tube #1 is tilted after 5 minutes to form a clot?
What is the purpose of adding 0.025 M CaCl2 in the Plasma Recalcification Test?
What is the component of the thromboplastin in the aPTT test?
What is the purpose of the Quick's Test/Prothrombin Time (PT)?
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What is the temperature at which samples are incubated in the Activated Clotting Time (ACT) test?
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What is the reference range of the aPTT test?
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What is the primary purpose of laboratory tests for secondary hemostasis?
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Which of the following factors is NOT part of the common pathway?
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What is the primary limitation of the Lee and White Whole Blood Coagulation Time method?
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What is the purpose of the blue mark on the capillary tube in the Capillary Tube Method?
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Which of the following is a problem associated with the intrinsic pathway?
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What is the purpose of breaking the capillary tube every 30 seconds in the Capillary Tube Method?
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Study Notes
Clotting Time Assessment
- Tilt tube #1 at 45° after 5 minutes to initiate clot formation, wait 30 seconds for interval.
- Clotting time observed in tube #3 is recorded.
Activated Clotting Time (ACT)
- Utilized for monitoring patients on heparin therapy.
- Incorporates an activator and samples incubated at 37°C.
- Normal reference values differ for general patients and those undergoing heparin therapy.
Plasma Recalcification Test
- Involves adding 0.025 M CaCl2 to the sample.
- Requires citrated Platelet Poor Plasma (PPP) or Platelet Rich Plasma (PRP) for testing.
- Reference values vary for PPP and PRP.
Activated Partial Thromboplastin Time (aPTT)
- Monitors efficacy of heparin therapy and screens for deficiencies in intrinsic and common clotting pathways.
- Thromboplastin consists of lipoprotein and phospholipids.
- Uses citrated PPP as the specimen.
- Main reagents include aPTT reagent with rabbit phospholipids, assorted activators, and 0.025 M CaCl2.
- Reference range must be established for patient assessment.
Extrinsic Pathway Evaluation
- Influenced by Vitamin K deficiencies and oral anticoagulants.
- Quick’s Test/Prothrombin Time (PT) is essential for monitoring oral anticoagulant therapy.
- Detects deficiencies related to Vitamin K-dependent clotting factors, excluding factor IX.
- Requires citrated PPP and PT reagent for testing.
- Reference range influenced by the International Sensitivity Index (ISI) with WHO standard set at 1.0.
Secondary Hemostasis Overview
- Assesses presence and functionality of coagulation factors in cascade reactions post-injury.
- Fibrin clot stabilization necessitates coagulation factors once a platelet plug forms.
Intrinsic and Common Pathways Assessment
- Intrinsic factors include XII, XI, IX, VIII, High Molecular Weight Kininogen (HMWK), and Prekallikrein (PK).
- Common factors encompass X, V, II, I, and XIII.
- Disorders in these pathways are often tied to liver diseases, circulating anticoagulants, and conditions like hypofibrinogenemia and lupus inhibitors.
Clotting Time Evaluation Methods
- Slide/Drop Method: For children, involves capillary puncture; starts timing after the second blood drop and waits 30 seconds for fibrin formation.
- Capillary Tube Method (Dale and Laidlaw’s Method): Blood is placed in a tube with no anticoagulant; check for fibrin formation every 30 seconds post skin puncture.
- Lee and White Whole Blood Coagulation Time: Less sensitive to factor deficiencies; begins timing when 1 mL of blood is transferred to individual tubes. Excessive sample agitation may lead to false results.
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Description
This quiz covers the laboratory tests used to evaluate secondary hemostasis, including the presence of coagulation factors and their function in the cascade reaction. It also explores the role of coagulation factors in stabilizing platelet plugs and forming fibrin clots.