MLHP 106 Hematology and Transfusion Science - Lesson 4 NOTES & Flashcards

100+ practice flashcards covering hemostasis, coagulation testing, PT/INR/aPTT, PPP preparation, sample handling, and related topics from MLHP 106 notes.

What are the four systems involved in hemostasis?

Blood vessels, platelets, blood coagulation factors, and fibrinolysis.

What is hemostasis?

The process of stopping bleeding, including clot formation and breakdown.

What is a fibrin clot also called?

A thrombus or hemostatic plug.

What are the two parts of hemostasis?

Primary hemostasis and secondary hemostasis.

What is the role of blood vessels in primary hemostasis?

Vasoconstriction to reduce blood flow at the damaged area.

What triggers platelet adhesion?

Exposure to collagen and tissue factor; platelets release calcium.

What is the major trigger of the coagulation cascade?

Tissue factor.

Why must tissue fluid not enter the collection tube?

To prevent activation of coagulation.

Define thrombocytopenia.

Severe decrease in circulating platelets.

Define thrombocytosis.

Severe increase in circulating platelets.

Which drug inhibits vitamin K dependent factors?

Warfarin (Coumadin).

Which drug inhibits thrombin and factor X?

Heparin.

Which drug inhibits platelet aggregation?

Aspirin.

Where are most coagulation factors produced?

In the liver.

What is needed for coagulation factors to work together?

Ionized calcium.

Name the three coagulation pathways.

Intrinsic, Extrinsic, and Common.

What is the end product of coagulation cascade?

A stable fibrin clot.

What are the major components of fibrinolysis?

Plasminogen and plasmin.

What activates plasminogen?

Tissue plasminogen activator (TPA).

What test detects fibrin degradation products?

D-Dimer.

What does PT assess?

The extrinsic and common pathways; used with INR to monitor warfarin.

What does aPTT assess?

The intrinsic and common pathways; used to monitor heparin therapy.

What does INR stand for?

International Normalized Ratio.

What is the normal PT reference range?

Approximately 10-13 seconds (lab/method varies).

What is the normal aPTT range?

Approximately 25-40 seconds.

What is the normal INR range?

1.0-1.4.

What INR range is commonly targeted for warfarin therapy?

2-3.

Which therapy is monitored by aPTT?

Heparin therapy.

Why is CaCl2 added in the aPTT test?

To reintroduce calcium and allow clotting to occur.

Why is sodium citrate used for coagulation testing?

It chelates calcium to prevent clotting during collection.

What is the required blood-to-anticoagulant ratio for coagulation studies?

9:1.

What does PPP stand for?

Platelet Poor Plasma.

How is PPP obtained?

Centrifuge citrate tube, transfer top 2/3 of plasma, re-centrifuge at 1500 g for 10 min, transfer top 3/4 to a new tube, label PPP, freeze.

How long should PT samples be stored at room temperature?

Within 24 hours.

How long should aPTT samples be tested after collection?

Within 4 hours.

What is the buffy coat?

The layer containing white blood cells; should not be disturbed when preparing PPP.

Why must PPP be platelet-poor?

To ensure accurate clotting times by removing platelets.

How long can PPP be stored at -20°C?

Up to 2 weeks.

How long can PPP be stored at -70°C if longer storage is required?

Long-term storage beyond 2 weeks.

What is a common pre-analytical error that can falsely prolong PT?

Tube not filled to minimum volume.

How does hemolysis affect PT results?

Can cause PT to be falsely shortened.

How can icterus or lipemia affect coagulation tests?

Can affect photo-optical methods.

What are common QC material handling guidelines for reagents?

Reconstitute QC materials; use within 48 hours after re-suspension; refrigerate as needed; follow exact dilutions; allow 15-30 minutes before use; some reagents require refrigeration.

What are the main clot detection methods?

Visual, mechanical/magnetic, and optical.

Describe the visual clot detection method.

Manual detection of clot formation in tubes.

Describe the mechanical/magnetic clot detection method.

Movement of a metal ball between magnets or probes; clot restricts movement.

Describe the optical clot detection method.

Detects fibrin formation by changes in optical density or turbidity.

What does sodium citrate do in the collection tube?

Chelates calcium to prevent clotting.

What is the purpose of a PT reagent?

Mimics tissue factor to trigger the extrinsic pathway.

What is the role of phospholipids in PT reagents?

Provide the surface for coagulation reactions.

What is the normal PT range in seconds?

Approximately 10-13 seconds.

What does ISI stand for in INR calculation?

International Sensitivity Index.

How is INR calculated?

Using PT result and ISI to standardize across labs.

Which pathway does PT measure most directly?

Extrinsic pathway.

Which pathway does aPTT measure most directly?

Intrinsic pathway.

What is the role of Vitamin K in coagulation testing?

Vitamin K dependent factors require vitamin K; deficiency can affect PT.

What is the purpose of Factor Assays?

Identify specific factor deficiencies (e.g., VIII or IX).

What does fibrinogen assay measure?

The ability of fibrinogen to form fibrin after exposure to high thrombin.

What does a D-Dimer test indicate clinically?

Fibrinolysis and clot breakdown.

What does a Thrombin Time (TT) measure?

Time for fibrinogen to be converted to fibrin.

What do Platelet Function Assays assess?

The ability of platelets to aggregate and promote clotting.

Which test is commonly used to monitor warfarin therapy?

PT/INR.

Which tests are used to monitor heparin therapy?

aPTT (PTT).

What triggers the extrinsic coagulation pathway?

Tissue factor activating the pathway.

What happens during platelet adhesion at injury?

Platelets adhere to exposed collagen and tissue factor, release calcium, and begin aggregation.

What is the role of vasoconstriction in hemostasis?

Narrowing of blood vessels to reduce blood loss.

What is von Willebrand factor (vWF) role?

Supports platelet adhesion/aggregation.

What is the difference between a thrombus and an embolus?

A thrombus is a clot in a vessel; an embolus travels in the circulation.

Which component is required for platelet aggregation?

Ionized calcium and fibrinogen.

What is the therapeutic INR range commonly used for warfarin?

2-3.

What is the purpose of gentle mixing for coagulation tubes?

To prevent platelet activation and erroneous results.

What is the difference between PPP and PRP?

PPP has very few platelets; PRP has high platelet concentration.

Which reagent is used to trigger the extrinsic pathway?

Tissue thromboplastin.

What does a normal PT imply about extrinsic/common pathways?

They are functioning within normal limits.

How can liver disease affect PT?

Typically prolongs PT due to reduced synthesis of factors.

What is a common lab requirement for reagent storage?

Many reagents have refrigerated sections and must be stored as per manufacturer.

How does Vitamin K deficiency show up in PT vs aPTT?

PT is often prolonged; aPTT may be affected less.

What is a common use of D-Dimer testing?

Detect clots breakdown products to indicate fibrinolysis.

In PT testing, what surface does the clot form on?

In the presence of tissue factor and phospholipids with calcium.

What does the 'platelet plug' represent?

The endpoint of primary hemostasis.

Which component is used to prevent clotting in collection tubes?

Sodium citrate (anticoagulant).

What is the role of the buffy coat in centrifuged samples?

Contains white blood cells; should not be disturbed when preparing PPP.

What is the function of tissue factor in coagulation?

Major trigger of the coagulation cascade (extrinsic pathway).

What is the D-Dimer used for clinically?

Indicates fibrinolysis and clot breakdown.

Which component forms the initial platelet plug?

Platelets in primary hemostasis.

What is the role of collagen in hemostasis?

Exposed collagen triggers platelet adhesion.

What is fibrin formed from?

Fibrin is formed when thrombin converts fibrinogen.

What is the intrinsic pathway factor set?

XI, IX, VIII, XII (with common factors X, V, II, I).

What is the extrinsic pathway factor?

Factor VII (and tissue factor).

What does aPTT evaluate?

Intrinsic and common pathways of coagulation.

What does PT evaluate?

Extrinsic and common pathways of coagulation.

Which collection tube is used for coagulation testing?

Light blue top with 3.2% buffered sodium citrate.

Why must collection tubes be handled gently?

To prevent platelet activation and erroneous results.

What is the standard instrument used in coagulation labs?

Automated coagulation analyzers.

Why is a 9:1 blood-to-anticoagulant ratio important?

Maintains accurate plasma-to-anticoagulant balance for testing.

Which component prevents clotting in collection tubes?

Sodium citrate (anticoagulant).

What is the buffy coat’s role in centrifuged samples?

Contains white blood cells; should not be disturbed when preparing PPP.

What is the role of tissue factor in coagulation?

Major trigger of the coagulation cascade (extrinsic pathway).

What is the clinical significance of D-Dimer testing?

Indicates fibrinolysis and clot breakdown.

Which test indicates the stability of a formed fibrin under time?

Thrombin Time (TT) measures fibrinogen to fibrin conversion.